Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods. Climate can be contrasted to weather, which is the present condition of these elements and their variations over shorter periods.

A region's climate is generated by the climate system, which has five components: Atmosphere, hydrosphere, cryosphere, land surface, and biosphere.

The climate of a location is affected by its latitude, terrain, and altitude, as well as nearby water bodies and their currents. Climates can be classified according to the average and the typical ranges of different variables, most commonly temperature and precipitation. The most commonly used classification scheme was originally developed by Wladimir Köppen. The Thornthwaite system, in use since 1948, incorporates evapotranspiration along with temperature and precipitation information and is used in studying animal species diversity and potential effects of climate changes. The Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region.

Paleoclimatology is the study of ancient climates. Since direct observations of climate are not available before the 19th century, paleoclimates are inferred from ''proxy variables'' that include non-biotic evidence such as sediments found in lake beds and ice cores, and biotic evidence such as tree rings and coral. Climate models are mathematical models of past, present and future climates. Climate change may occur over long and short timescales from a variety of factors; recent warming is discussed in global warming.

Definition

Climate (from Ancient Greek ''klima'', meaning ''inclination'') is commonly defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The Intergovernmental Panel on Climate Change (IPCC) glossary definition is:

''''

The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get." Over historical time spans there are a number of nearly constant variables that determine climate, including latitude, altitude, proportion of land to water, and proximity to oceans and mountains. These change only over periods of millions of years due to processes such as plate tectonics. Other climate determinants are more dynamic: the thermohaline circulation of the ocean leads to a 5 °C (9 °F) warming of the northern Atlantic Ocean compared to other ocean basins. Other ocean currents redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.

Climate classification

There are several ways to classify climates into similar regimes. Originally, climes were defined in Ancient Greece to describe the weather depending upon a location's latitude. Modern climate classification methods can be broadly divided into ''genetic'' methods, which focus on the causes of climate, and ''empiric'' methods, which focus on the effects of climate. Examples of genetic classification include methods based on the relative frequency of different air mass types or locations within synoptic weather disturbances. Examples of empiric classifications include climate zones defined by plant hardiness, evapotranspiration, or more generally the Köppen climate classification which was originally designed to identify the climates associated with certain biomes. A common shortcoming of these classification schemes is that they produce distinct boundaries between the zones they define, rather than the gradual transition of climate properties more common in nature.

Bergeron and Spatial Synoptic

The simplest classification is that involving air masses. The Bergeron classification is the most widely accepted form of air mass classification. Air mass classification involves three letters. The first letter describes its moisture properties, with c used for continental air masses (dry) and m for maritime air masses (moist). The second letter describes the thermal characteristic of its source region: T for tropical, P for polar, A for Arctic or Antarctic, M for monsoon, E for equatorial, and S for superior air (dry air formed by significant downward motion in the atmosphere). The third letter is used to designate the stability of the atmosphere. If the air mass is colder than the ground below it, it is labeled k. If the air mass is warmer than the ground below it, it is labeled w. While air mass identification was originally used in weather forecasting during the 1950s, climatologists began to establish synoptic climatologies based on this idea in 1973.

Based upon the Bergeron classification scheme is the Spatial Synoptic Classification system (SSC). There are six categories within the SSC scheme: Dry Polar (similar to continental polar), Dry Moderate (similar to maritime superior), Dry Tropical (similar to continental tropical), Moist Polar (similar to maritime polar), Moist Moderate (a hybrid between maritime polar and maritime tropical), and Moist Tropical (similar to maritime tropical, maritime monsoon, or maritime equatorial).

Köppen

The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. These primary types are A, tropical; B, dry; C, mild mid-latitude; D, cold mid-latitude; and E, polar. The five primary classifications can be further divided into secondary classifications such as rain forest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, steppe, subarctic climate, tundra, polar ice cap, and desert.

Rain forests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between and . Mean monthly temperatures exceed during all months of the year.

A monsoon is a seasonal prevailing wind which lasts for several months, ushering in a region's rainy season. Regions within North America, South America, Sub-Saharan Africa, Australia and East Asia are monsoon regimes.

A tropical savanna is a grassland biome located in semiarid to semi-humid climate regions of subtropical and tropical latitudes, with average temperatures remain at or above year round and rainfall between and a year. They are widespread on Africa, and are found in India, the northern parts of South America, Malaysia, and Australia.

The humid subtropical climate zone where winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and from occasional tropical cyclones. Humid subtropical climates lie on the east side continents, roughly between latitudes 20° and 40° degrees away from the equator.

A humid continental climate is marked by variable weather patterns and a large seasonal temperature variance. Places with more than three months of average daily temperatures above and a coldest month temperature below and which do not meet the criteria for an arid or semiarid climate, are classified as continental.

An oceanic climate is typically found along the west coasts at the middle latitudes of all the world's continents, and in southeastern Australia, and is accompanied by plentiful precipitation year round.

The Mediterranean climate regime resembles the climate of the lands in the Mediterranean Basin, parts of western North America, parts of Western and South Australia, in southwestern South Africa and in parts of central Chile. The climate is characterized by hot, dry summers and cool, wet winters.

A steppe is a dry grassland with an annual temperature range in the summer of up to and during the winter down to .

A subarctic climate has little precipitation, and monthly temperatures which are above for one to three months of the year, with permafrost in large parts of the area due to the cold winters. Winters within subarctic climates usually include up to six months of temperatures averaging below .

Tundra occurs in the far Northern Hemisphere, north of the taiga belt, including vast areas of northern Russia and Canada.

A polar ice cap, or polar ice sheet, is a high-latitude region of a planet or moon that is covered in ice. Ice caps form because high-latitude regions receive less energy as solar radiation from the sun than equatorial regions, resulting in lower surface temperatures.

A desert is a landscape form or region that receives very little precipitation. Deserts usually have a large diurnal and seasonal temperature range, with high daytime temperatures (in summer up to 45 °C or 113 °F), and low nighttime temperatures (in winter down to 0 °C; 32 °F) due to extremely low humidity. Many deserts are formed by rain shadows, as mountains block the path of moisture and precipitation to the desert.

Thornthwaite

Devised by the American climatologist and geographer C. W. Thornthwaite, this climate classification method monitors the soil water budget using evapotranspiration. It monitors the portion of total precipitation used to nourish vegetation over a certain area. It uses indices such as a humidity index and an aridity index to determine an area's moisture regime based upon its average temperature, average rainfall, and average vegetation type. The lower the value of the index in any given area, the drier the area is.

The moisture classification includes climatic classes with descriptors such as hyperhumid, humid, subhumid, subarid, semi-arid (values of −20 to −40), and arid (values below −40). Humid regions experience more precipitation than evaporation each year, while arid regions experience greater evaporation than precipitation on an annual basis. A total of 33 percent of the Earth's landmass is considered either arid of semi-arid, including southwest North America, southwest South America, most of northern and a small part of southern Africa, southwest and portions of eastern Asia, as well as much of Australia. Studies suggest that precipitation effectiveness (PE) within the Thornthwaite moisture index is overestimated in the summer and underestimated in the winter. This index can be effectively used to determine the number of herbivore and mammal species numbers within a given area. The index is also used in studies of climate change.

Thermal classifications within the Thornthwaite scheme include microthermal, mesothermal, and megathermal regimes. A microthermal climate is one of low annual mean temperatures, generally between and which experiences short summers and has a potential evaporation between and . A mesothermal climate lacks persistent heat or persistent cold, with potential evaporation between and . A megathermal climate is one with persistent high temperatures and abundant rainfall, with potential annual evaporation in excess of .

Record

Modern

Details of the modern climate record are known through the taking of measurements from such weather instruments as thermometers, barometers, and anemometers during the past few centuries. The instruments used to study weather over the modern time scale, their known error, their immediate environment, and their exposure have changed over the years, which must be considered when studying the climate of centuries past.

Paleoclimatology

Paleoclimatology is the study of past climate over a great period of the Earth's history. It uses evidence from ice sheets, tree rings, sediments, coral, and rocks to determine the past state of the climate. It demonstrates periods of stability and periods of change and can indicate whether changes follow patterns such as regular cycles.

Climate change

Climate change is the variation in global or regional climates over time. It reflects changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth, external forces (e.g. variations in sunlight intensity) or, more recently, human activities.

In recent usage, especially in the context of environmental policy, the term "climate change" often refers only to changes in modern climate, including the rise in average surface temperature known as global warming. In some cases, the term is also used with a presumption of human causation, as in the United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations.

Earth has undergone periodic climate shifts in the past, including four major ice ages. These consisting of glacial periods where conditions are colder than normal, separated by interglacial periods. The accumulation of snow and ice during a glacial period increases the surface albedo, reflecting more of the Sun's energy into space and maintaining a lower atmospheric temperature. Increases in greenhouse gases, such as by volcanic activity, can increase the global temperature and produce an interglacial. Suggested causes of ice age periods include the positions of the continents, variations in the Earth's orbit, changes in the solar output, and volcanism.

Climate models

Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the earth with outgoing energy as long wave (infrared) electromagnetic radiation from the earth. Any imbalance results in a change in the average temperature of the earth.

The most talked-about applications of these models in recent years have been their use to infer the consequences of increasing greenhouse gases in the atmosphere, primarily carbon dioxide (see greenhouse gas). These models predict an upward trend in the global mean surface temperature, with the most rapid increase in temperature being projected for the higher latitudes of the Northern Hemisphere.

Models can range from relatively simple to quite complex:

Simple radiant heat transfer model that treats the earth as a single point and averages outgoing energy

this can be expanded vertically (radiative-convective models), or horizontally

finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.

See also

Atmosphere

Climate Prediction Center

Ecosystem

Effect of sun angle on climate

Greenhouse effect

List of climate scientists

Microclimate

National Climatic Data Center

Outline of meteorology

Solar variation

Temperature extreme

Tropical marine climate

Weather

References

External links

The Earth's climate – Centre national de la recherche scientifique (CNRS – France)

NOAA Climate Services Portal

IGBP Climate-change Index

The Economics of Climate-based Data NOAA Economics

AgClimate IFAS

Climate Models and modeling groups

Climate Prediction Project

WorldClimate

ESPERE Climate Encyclopaedia

Climate index and mode information regarding the Arctic

A current view of the Bering Sea Ecosystem and Climate

Climate: Data and charts for world and US locations

MIL-HDBK-310, Global Climate Data U.S. Department of Defense Data on natural environmental starting points for engineering analyses to derive environmental design criteria

ClimateDiagrams.com Climate diagrams for over 3 000 weather stations and different climate periods from around the world. Users can create their own diagrams with their own data.

IPCC Data Distribution Centre Climate data and guidance on its use.

Category:Basic meteorological concepts and phenomena Category:Greek loanwords

af:Klimaat ar:مناخ an:Clima az:İqlim bn:জলবায়ু ba:Климат be:Клімат be-x-old:Клімат bar:Klima bs:Klima bg:Климат ca:Clima ceb:Klima cs:Podnebí cy:Hinsawdd da:Klima de:Klima et:Kliima el:Κλίμα es:Clima eo:Klimato eu:Klima fa:اقلیم fr:Climat fy:Klimaat ga:Aeráid gl:Clima ko:기후 hi:जलवायु hr:Klima io:Klimato id:Iklim ia:Climate is:Loftslag it:Clima he:אקלים jv:Iklim krc:Климат ka:კლიმატი kk:Климат ht:Klima la:Clima lv:Klimats lt:Klimatas hu:Éghajlat mk:Клима mg:Toe-tany ms:Iklim mwl:Clima mn:Уур амьсгал my:ရာသီဥတု nl:Klimaat ja:気候 no:Klima nn:Klima oc:Clima pnb:کلائمیٹ pap:Klima pl:Klimat pt:Clima kaa:Klimat ro:Climă rue:Клімат ru:Климат sco:Climate stq:Klima sq:Klima scn:Clima simple:Climate sk:Podnebie sl:Podnebje sr:Клима sh:Klima fi:Ilmasto sv:Klimat ta:தட்பவெப்பநிலை tt:Климат th:ภูมิอากาศ tg:Иқлим tr:İklim uk:Клімат za:Heiqhaeuh vec:Clima vi:Khí hậu fiu-vro:Kliima war:Klema zh-yue:氣候 zh:氣候

Name	Naomi Oreskes
Fields	Science History, Economic geology
Workplaces	Stanford University U.S. Environmental Protection Agency Dartmouth College Harvard University New York University University of California San Diego
Alma mater	Imperial College, University of London Stanford University
Signature
Footnotes	}}

Naomi Oreskes is an American science historian, and Professor of History and Science Studies at the University of California San Diego. She has worked on studies of geophysics, environmental issues such as global warming, and the history of science. In 2010, Oreskes co-authored ''Merchants of Doubt'' which identified some parallels between the climate change debate and earlier public controversies.

Background

Oreskes graduated from Stuyvesant High School in 1976. She received her BSc degree in Mining Geology from the Royal School of Mines of Imperial College, University of London in 1981, and worked as a Research Assistant in the Geology Department and as a Teaching Assistant in the departments of Geology, Philosophy and Applied Earth Sciences at Stanford University starting in 1984. She received her PhD degree in the Graduate Special Program in Geological Research and History of Science at Stanford in 1990. She received a National Science Foundation's Young Investigator Award in 1994.

She has worked as a consultant for the United States Environmental Protection Agency and U.S National Academy of Sciences, and has also taught at Dartmouth, Harvard and New York University (NYU). She is also a member of the History of Science Society. She is the author or has contributed to a number of essays and technical reports in economic geology and science history in addition to several books:

''The Rejection of Continental Drift: Theory and Method in American Earth Science'', Oxford University Press, 1999, ISBN 0-19-511733-6

''Plate Tectonics: An Insider’s History of the Modern Theory of the Earth'', Edited with Homer Le Grand, Westview Press, 2003, ISBN 0-8133-4132-9

''Perspectives on Geophysics,'' Special Issue of Studies in the History and Philosophy of Modern Physics, 31B, Oreskes, Naomi and James R. Fleming, eds., 2000.

''Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming'', Naomi Oreskes and Erik M. Conway, Bloomsbury Press, 2010

Oreskes is currently the Provost of the Sixth College at the University of California, San Diego.

Science and society essay

Oreskes wrote an essay on science and society ''Beyond the Ivory Tower: The Scientific Consensus on Climate Change'' in the journal Science in December 2004.

In the essay she reported an analysis of “928 abstracts, published in refereed scientific journals between 1993 and 2003 and published in the ISI database with the keywords ‘global climate change’”. The essay stated the analysis was to test the hypothesis that the drafting of reports and statements by societies such as the Intergovernmental Panel on Climate Change, American Association for the Advancement of Science and National Academy of Sciences might downplay legitimate dissenting opinions on anthropogenic climate change. After the analysis, she concluded that 75 percent of the examined abstracts either explicitly or implicitly backed the consensus view, while none directly dissented from it. The essay received a great deal of media attention from around the world and has been cited by many prominent persons such as Al Gore in the movie ''An Inconvenient Truth''.

In 2007, Oreskes expanded her analysis, stating that approximately 20 percent of abstracts explicitly endorsed the consensus on climate change that: "Earth's climate is being affected by human activities". In addition, 55 percent of abstracts "implicitly" endorsed the consensus by engaging in research to characterize the ongoing and/or future impact of climate change (50 percent of abstracts) or to mitigate predicted changes (5 percent). The remaining 25 percent focused on either paleoclimate (10%) or developing measurement techniques (15%); Oreskes did not classify these as taking a position on contemporary global climate change.

Merchants of Doubt

''Merchants of Doubt'' is a 2010 book by Naomi Oreskes and Erik M. Conway. Oreskes and Conway, both American science historians, identify some remarkable parallels between the climate change debate and earlier controversies over tobacco smoking, acid rain and the hole in the ozone layer. They argue that spreading doubt and confusion was the basic strategy of those opposing action in each case. In particular, Fred Seitz, Fred Singer, and a few other contrarian scientists joined forces with conservative think tanks and private corporations to challenge the scientific consensus on many contemporary issues.

The Marshall Institute has been critical of the book, but most other reviewers received it favorably. One reviewer said that ''Merchants of Doubt'' is exhaustively researched and documented, and may be one of the most important books of 2010. Another reviewer saw the book as his choice for best science book of the year.

Selected awards, honors, and fellowships

George Sarton Award Lecture, American Association for the Advancement of Science, 2004

American Philosophical Society Sabbatical Fellowship, 2001-2002.

National Science Foundation Young Investigator Award, 1994-1999.

National Endowment for the Humanities Fellowship for University Teachers, 1993-94.

Society of Economic Geologists Lindgren Prize for outstanding work by a young scientist, 1993.

Ritter Memorial Fellowship in History of Marine Sciences, Scripps Institution of Oceanography, 1994.

Listed, Who’s Who in American Science and Engineering, Who’s Who in the West.

References

External links

Oreskes page at UCSD

Category:Alumni of Imperial College London Category:American non-fiction environmental writers Category:Dartmouth College faculty Category:Living people Category:Harvard University faculty Category:New York University faculty Category:Stanford University alumni Category:Stuyvesant High School alumni Category:University of California, San Diego faculty Category:Women earth scientists Category:Year of birth missing (living people) Category:Place of birth missing (living people) Category:American historians

ar:ناومي أوراسكس de:Naomi Oreskes nl:Naomi Oreskes no:Naomi Oreskes

Honorific-prefix	The Honourable Senator
Name	Nicholas Minchin
Honorific-suffix	LLB BEc
Office	Australian Senator for South Australia
Term start	1 July 1993
Term end	30 June 2011
Preceded	Graham Maguire
Succeeded	Incumbent
Birth date	April 15, 1953
Birth place	Sydney
Party	Liberal Party of Australia
Spouse	Kerry Minchin
Occupation	Solicitor
Alma mater	Australian National University
Website	}}

Nicholas Hugh "Nick" Minchin (born 15 April 1953) is a former Australian politician, serving as a Liberal member of the Australian Senate representing South Australia from July 1993 to June 2011, and a former cabinet minister in the Howard Government.

Early life and education

Minchin was born in Sydney and was educated at the Australian National University, Canberra, where he gained degrees in law and economics. He was a solicitor before entering politics.

Political career

Minchin was a staff member for the Liberal Party's Federal Secretariat 1977–83, Deputy Federal Director of the Liberal Party in 1983, South Australian State Director and Campaign Director of the Liberal Party 1985–93. On 1 July 1993, Minchin was elected to the Australian Senate for South Australia.

Minchin was a member of the Opposition Shadow Ministry 1994–96, holding the position of Parliamentary Secretary to the Leader of the Opposition, John Howard. He was Parliamentary Secretary to the Prime Minister John Howard 1996–97, Special Minister of State and Minister Assisting the Prime Minister 1997–98, and Minister for Industry, Science and Resources 1998–2001, with a seat in the Cabinet. He was Minister for Finance and Administration from November 2001 until the defeat of the Howard government at the 2007 federal election. Until that election he also held the posts of Leader of the Government in the Senate and Vice-President of the Executive Council.

Minchin was a right faction leader in the Liberal Party, and supported the abolition of Australia's compulsory voting system, on the stated basis that "compulsory voting is a fundamental breach of ... civil liberties". He supported states' rights in Cabinet. As Leader of the Government in the Senate he played a significant role in pursuing and defending its reforms of the Senate committee system, implemented in 2006 following his government's success in securing a majority of Senate seats at the 2004 election.

Retirement

Minchin announced on 24 March 2010 that he would not be contesting his Senate seat at the next Australian federal election. His term ended on 30 June 2011. He also resigned his Opposition portfolios and addressed the media saying that: "I love politics. This is not an easy decision to make ... when something like that happens and when one of your children, quite frankly, has a near-death experience, it does make you reassess your life and your priorities". His son, Oliver was seriously injured in a boat accident while training with the Australian Defence Force Academy in February.

Policy positions

Minchin has been a strong proponent of privatisation and wholesale labour market deregulation. He has defended the full privatisation of Telstra, and argued that the Commonwealth should sell its Telstra shares to buy a portfolio of other income-earning investments rather than spend the profits on national infrastructure.

In March 2006, Minchin received extensive media coverage when he highlighted the dilemma his government faced in the field of industrial relations and aired his views about future policy proposals. Speaking at a conference of the H. R. Nicholls Society where he told the audience that the coalition "knew its reform to WorkChoices were not popular but the process of change must continue", and that "there is still a long way to go... awards, the IR commission, all the rest of it...", he went on to say "The fact is the great majority of the Australian people do not support what we are doing on industrial relations. They violently disagree."

Tobacco sceptic

In 1995 Minchin submitted a dissenting Senate report on the tobacco industry and the costs of tobacco-related illness that disputed the Committee's statements that it believes cigarettes are addictive and that passive smoking is harmful. Minchin claimed the tobacco industry was over-regulated. He also disagreed with the conclusions about the addictiveness of nicotine and the harmfulness of passive smoking:

A 2009 article in The Australian drew parallels between his stance on tobacco and his stance as a climate change skeptic.

Climate-change view

In a March 2007 letter, Minchin expressed doubts that climate change is caused by human activity. In the letter, Minchin cites the writings of the Canadian newspaper columnist Lawrence Solomon, who in turn cites the disputed theories of Danish scientist Henrik Svensmark. Of the effectiveness and sensibility of ETS bill, Minchin said that it is unsound and an "abomination", and of the motives behind its tabling that "Mr Rudd's arrogance and vanity in wanting to lead the world in cutting CO₂ emissions is really sickening"

Minchin campaigned against an emissions trading scheme (ETS) bill.

On 22 September 2008, the parliamentary leader of the Liberal Party, Malcolm Turnbull, appointed Minchin as Shadow Minister for Broadband, Communications and the Digital Economy, and Leader of the Opposition in the Senate. Minchin had been previously Shadow Minister for Defence. However on 26 November 2009, Minchin resigned from the shadow cabinet in protest at Turnbull's position on the government's emissions trading scheme.

When Turnbull was subsequently defeated for the Liberal Party leadership by Tony Abbott, Turnbull stated on ABC Radio: "As Tony [Abbott] observed on one occasion, 'climate change is crap', or if you consider his mentor, Senator Minchin, the world is not warming, it's cooling and the climate change issue is part of a vast left-wing conspiracy to deindustrialise the world".

References

Bibliography

Minchin, N. (1996) 'A Denial of Rights, A Detriment to Democracy', ''The Parliamentarian'', 77(3) : 244–248.

Category:1953 births Category:Living people Category:Liberal Party of Australia politicians Category:Members of the Cabinet of Australia Category:Members of the Australian Senate Category:Australian monarchists Category:Members of the Australian Senate for South Australia Category:People educated at Knox Grammar School Category:Politicians from Sydney Category:Australian National University alumni fr:Nick Minchin

Name	James E. Hansen
Birth date	March 29, 1941
Birth place	Denison, Iowa
Fields	Atmospheric Physics
Workplaces	The NASA Goddard Institute for Space Studies
Alma mater	University of Iowa
Known for	Radiative transfer, Planetary atmospheres, Climate models
Influences	James Van Allen
Awards	United States National Academy of Sciences, Carl-Gustaf Rossby Research Medal
Signature
Footnotes	}}

James E. Hansen (born March 29, 1941) heads the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland. He has held this position since 1981. He is also an adjunct professor in the Department of Earth and Environmental Sciences at Columbia University.

After graduate school, Hansen continued his work with radiative transfer models, attempting to understand the Venusian atmosphere. Later he applied and refined these models to understand the Earth's atmosphere, in particular, the effects that aerosols and trace gases have on Earth's climate. Hansen's development and use of global climate models has contributed to the further understanding of the Earth's climate.

Hansen is best known for his research in the field of climatology, his testimony on climate change to congressional committees in 1988 that helped raise broad awareness of global warming, and his advocacy of action to limit the impacts of climate change. In recent years, Hansen has become an activist for action to mitigate the effects of climate change, which on a few occasions has led to his arrest.

In 2009 his first book, ''Storms of My Grandchildren'', was published.

Early life and education

Hansen was born in Denison, Iowa. He was trained in physics and astronomy in the space science program of James Van Allen at the University of Iowa. He obtained a B.A. in Physics and Mathematics with highest distinction in 1963, an M.S. in Astronomy in 1965 and a Ph.D. in Physics, in 1967, all three degrees from the University of Iowa. He participated in the NASA graduate traineeship from 1962 to 1966 and, at the same time, between 1965 and 1966, he was a visiting student at the Institute of Astrophysics at the University of Kyoto and in the Department of Astronomy at the University of Tokyo. Hansen then began work at the Goddard Institute for Space Studies in 1967.

Research and publications

As a college student at the University of Iowa, Hansen was attracted to science and the research done by James Van Allen's space science program in the physics and astronomy department. A decade later, his focus shifted to planetary research that involved trying to understand the climate change on earth that will result from anthropogenic changes of the atmospheric composition.

Hansen has stated that one of his research interests is radiative transfer in planetary atmospheres, especially the interpretation of remote sensing of the Earth's atmosphere and surface from satellites. Because of the ability of satellites to monitor the entire globe, they may be one of the most effective ways to monitor and study global change. His other interests include the development of global circulation models to help understand the observed climate trends, and diagnosing human impacts on climate.

Atmosphere of Venus

In the late 1960s and early 1970s, Hansen published several papers on the planet Venus following his Ph.D. dissertation. Venus has a high brightness temperature in the radio frequencies compared to the infrared. Hansen proposed that the hot surface was the result of aerosols trapping the internal energy of the planet. More recent studies have suggested that several billion years ago Venus's atmosphere was much more like Earth's than it is now, and that there were probably substantial quantities of liquid water on the surface, but a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse gases in its atmosphere.

Hansen continued his study of Venus by looking at the composition of its clouds. He looked at the near-infrared reflectivity of ice clouds, compared them to observations of Venus, and found that they qualitatively agreed. He also was able to use a radiative transfer model to establish an upper limit to the size of the ice particles if the clouds were actually made of ice. Evidence published in the early 1980s showed that the clouds consist mainly of sulfur dioxide and sulfuric acid droplets.

By 1974, the composition of Venus' clouds had not yet been determined, with many scientists proposing a wide variety of compounds including liquid water and aqueous solutions of ferrous chloride. Hansen and Hovenier used the polarization of sunlight reflected from the planet to establish that the clouds were spherical, and had a refractive index and cloud drop effective radius which eliminated all of the proposed cloud types except sulfuric acid. Kiyoshi Kawabata and Hansen expanded upon this work by looking at the variation of polarization on Venus. They found that the visible clouds are a diffuse haze rather than a thick cloud, which confirmed the same results obtained from transits across the sun.

The Pioneer Venus project was launched in May 1978 and reached Venus late that same year. Hansen collaborated with Larry Travis and other colleagues in a 1979 ''Science'' article that reported on the development and variability of clouds in the ultraviolet spectrum. They conclude that there are at least three different cloud materials that contribute to the images: a thin haze layer, sulfuric acid clouds, and an unknown ultraviolet absorber below the sulfuric acid cloud layer. The linear polarization data obtained from the same mission confirmed that the low- and mid-level clouds were sulfuric acid with radius of about 1 micrometer. Above the cloud layer was a layer of submicrometre haze.

Global temperature analysis

The first GISS global temperature analysis was published in 1981. Hansen and his co-author analyzed the surface air temperature at meteorological stations focusing on the years from 1880 to 1985. Temperatures for stations closer together than 1000 kilometers were shown to be highly correlated, especially in the mid-latitudes, which provided a way to combine the station data to provided accurate long-term variations. They conclude that global mean temperatures can be determined even though meteorological stations are typically in the Northern hemisphere and confined to continental regions. Warming in the past century was found to be , with warming similar in both hemispheres. When the analysis was updated in 1988, the four warmest years on record were all in the 1980s. The two warmest years were 1981 and 1987.

With the 1991 eruption of Mount Pinatubo, 1992 saw a cooling in the global temperatures. There was speculation that this would cause the next couple years to be cooler because of the large serial correlation in the global temperatures. Bassett and Lin found the statistical odds of a new temperature record to be small. Hansen countered by saying that having insider information shifts the odds to those that know the physics of the climate system, and that whether there is a new temperature record depends upon the particular data set used.

The temperature data was updated in 1999 to report that 1998 was the warmest year since the instrumental data began in 1880. They also found that the rate of temperature change was larger than any time in instrument history, and conclude that the recent El Nino was not totally responsible for the large temperature anomaly in 1998. In spite of this, the United States had seen a smaller degree of warming, and a region in the eastern U.S. and the western Atlantic Ocean had actually cooled slightly.

2001 saw a major update to how the temperature was calculated. It incorporated corrections due to the following reasons: time-of-observation bias, station history changes, classification of rural/urban stations, the urban adjustment based on satellite measurements of night light intensity, and relying more on rural station than urban. Evidence was found of local urban warming in urban, suburban and small-town records.

The anomalously high global temperature in 1998 due to El Niño resulted in a brief drop in subsequent years. However, a 2001 Hansen report in the journal ''Science'' states that global warming continues, and that the increasing temperatures should stimulate discussions on how to slow global warming. The temperature data was updated in 2006 to report that temperatures are now warmer than a century ago, and conclude that the recent global warming is a real climate change and not an artifact from the urban heat island effect. The regional variation of warming, with more warming in the higher latitudes, is further evidence of warming that is anthropogenic in origin.

In 2007, Stephen McIntyre notified GISS that many of the U.S. temperature records from the Historical Climatology Network (USHCN) displayed a discontinuity around the year 2000. NASA corrected the computer code used to process the data and credited McIntyre with pointing out the flaw. Hansen indicated that he felt that several news organizations had overreacted to this mistake. In 2010, Hansen published a paper entitled "Global Surface Temperature Change" describing current global temperature analysis.

Black carbon

Hansen has also contributed toward the understanding of black carbon on regional climate. In recent decades, northern China has experienced increased drought, and southern China has received increased summer rain resulting in a larger number of floods. Southern China has had a decrease in temperatures while most of the world has warmed. In a paper with Menon and colleagues, through the use of observations and climate models results, they conclude that the black carbon heats the air, increases convection and precipitation, and leads to larger surface cooling than if the aerosols were sulfates.

A year later, Hansen teamed with Makiko Sato to publish a study on black carbon using the global network of AERONET sun photometers. While the location of the AERONET instruments did not represent a global sample, they could still be used to validate global aerosol climatologies. They found that most aerosol climatologies underestimated the amount of black carbon by a factor of at least 2. This corresponds to an increase in the climate forcing of around , which they hypothesize is partially offset by the cooling of non-absorbing aerosols.

Estimations of trends in black carbon emissions show that there was a rapid increase in the 1880s after the start of the Industrial Revolution, and a leveling off from 1900-1950 as environmental laws were enacted. China and India have recently increased their emissions of black carbon corresponding to their rapid development. The emissions from the United Kingdom were estimated using a network of stations that measured black smoke and sulfur dioxide. They report that atmospheric black carbon concentrations have been decreasing since the beginning of the record in the 1960s, and that the decline was faster than the decline in black carbon producing fuel use.

A 2007 paper used the GISS climate model in an attempt to determine the origin of black carbon in the arctic. Much of the arctic aerosol comes from south Asia. Countries such as the United States and Russia have a lower contribution that previously assumed.

Dangerous anthropogenic interference

The United Nations Framework Convention on Climate Change is an international environmental treaty that was aimed at stabilizing greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

In 2003 Hansen wrote a paper called ''Can We Defuse the Global Warming Time Bomb?'' where he argues that human-caused forces on the climate are now greater than natural ones, and that this, over a long time period, can cause large climate changes. He further states that a lower limit on “dangerous anthropogenic interference” is set by the stability of the Greenland and Antarctic ice sheets. His view on actions to mitigate climate change is that "halting global warming requires urgent, unprecedented international cooperation, but the needed actions are feasible and have additional benefits for human health, agriculture and the environment."

In a 2004 presentation at the University of Iowa, Hansen announced that he was told by high-ranking government officials not to talk about how anthropogenic influence could have a dangerous effect on climate because it's not understood what dangerous means, or how human are actually affecting climate. He describes this as a Faustian bargain because atmospheric aerosols have health risks, and should be reduced, but doing so will effectively increase the warming effects from .

Hansen and coauthors propose that the global mean temperature is a good tool to diagnose dangerous anthropogenic interference with the climate system. Two elements are particularly important when discussing dangerous anthropogenic interference: sea level rise and the extinction of species. They describe a business as usual scenario, which has greenhouse gases growing at approximately 2% per year, and an alternate scenario, in which greenhouse gases concentrations decline. Under the alternate scenario, sea levels could rise by 1 meter per century, causing problems due to the dense population in coastal areas. But this would be minor compared to the 10 meter increase in sea level under the business as usual scenario. Hansen describes the situation with species extinction similarly to sea level rise. Assuming the alternate scenario, the situation is not good, but it is much worse for business as usual.

The concept of dangerous anthropogenic interference was clarified in a 2007 paper. They find that further warming of 1 °C would be highly disruptive to humans. An alternative scenario would keep the warming to below this if climate sensitivity were below 3 °C for doubled . The conclusion is that levels above 450 ppm are considered dangerous, but that reduction in non- greenhouse gases can provide temporary relief from drastic cuts. Further, they find that arctic climate change has been forced by non- constituents as much as . They caution that prompt action is needed to slow growth and prevent a dangerous anthropogenic interference.

Climate model development and projections

Vilhelm Bjerknes began the modern development of the general circulation model in the early 20th century. The progress of numerical modeling was slow due to the slow speed of early computers and the lack of adequate observations. It wasn't until the 1950s that the numerical models were getting close to being realistic. Hansen's first contribution to numerical climate models came with the 1974 publication of the GISS model. He and his colleagues claimed that the model was successful in simulating the major features of sea-level pressure and 500mb heights in the North American region.

A 1981 ''Science'' publication by Hansen and a team of scientists at Goddard concluded that carbon dioxide in the atmosphere would lead to warming sooner than previously predicted. They used a one-dimensional radiative-convective model that calculates temperature as a function of height. They reported that the results from the 1D model are similar to the more complex 3D models, and can simulate basic mechanisms and feedbacks. Hansen predicted that temperatures would rise out of the climate noise by the 1990s, much earlier than predicted by other researches. He also predicted that it would be difficult to convince politicians and the public to react.

By the early 1980s the computational speed of computers, along with refinements in climate models, allowed longer experiments. The models now included physics beyond the previous equations, such as convection schemes, diurnal changes, and snow depth calculations. The advances in computational efficiency, combined with the added physics, meant the GISS model I could be run for five years. They showed that global climate can be simulated reasonably well with a grid-point resolution as coarse as 1000 kilometers.

The first climate prediction computed from a general circulation model that was published by Hansen was in 1988, the same year as his well-known Senate testimony. It used the second generation of the GISS model to estimate the change in mean surface temperature based on a variety of scenarios of future greenhouse gas emissions. Hansen concluded that global warming would be evident within the next few decades, and that it would result in temperatures at least as high as during the Eemian. He argued that, if the temperature rises above the 1950-1980 mean for a few years, it is the "smoking gun" pointing to human-caused global warming.

In 2006, Hansen and colleagues compared the observations with the projections made by Hansen in his 1988 testimony before the United States Congress. They described the intermediate scenario as the most likely, and that real-world greenhouse gas forcing has been closest to this scenario. It contained the effects of three volcanic eruptions in the fifty year projections, with one in the 1995, whereas the recent Mount Pinatubo eruption was in 1991. They found that the observed warming was similar to two of the three scenarios. The warming rates of the two most modest warming scenarios are nearly the same through the year 2000, and they were unable to provide a precise model assessment. They did note that the agreement between the observations and the intermediate scenario was accidental because the climate sensitivity used was higher than current estimates.

A year later, he joined with Rahmstorf and colleagues comparing climate projections with observations. The comparison is done from 1990 through January 2007 against physics-based models that are independent from the observations after 1990. They show that the climate system may be responding faster than the models indicate. Rahmstorf and coauthors show concern that sea levels are rising at the high range of the IPCC projections, and that it is due to thermal expansion and not from the Greenland or Antarctic ice sheets.

Following the launch of spacecraft capable of determining temperatures, Roy Spencer and John Christy published the first version of their satellite temperature measurements in 1990. Contrary to climate models and surface measurements, their results showed a cooling in the troposphere. In 1998, Wentz and Schabel determined that orbital decay had an effect on the derived temperatures. Hansen compared the corrected troposphere temperatures with the results of the published GISS model, and concluded that the model is in good agreement with the observations, noting that the satellite temperature data had been the last holdout of global warming denialists, and that the correction of the data would result in a change from discussing whether global warming was occurring to what is the rate of global warming, and what should be done about it.

Hansen has continued the development and diagnostics of climate models. For instance, he has helped look at the decadal trends in tropopause height, which could be a useful tool for determining the human "fingerprint" on climate. , the current version of the GISS model is Model E. This version has seen improvements in many areas, including upper-level winds, cloud height, and precipitation. This model still has problems with regions of marine stratocumulus clouds. A later paper showed that the model's main problems are having too weak of an ENSO-like variability, and poor sea ice modeling, resulting in too little ice in the Southern Hemisphere and too much in the Northern Hemisphere.

Climate forcings, feedbacks, and sensitivity

In 2000 he authored a paper called ''Global warming in the twenty-first century: an alternative scenario'' in which he presents a more optimistic way of dealing with global warming focusing on non-CO₂ gases and black carbon in the short run, giving more time to make reductions in fossil fuel emissions. He notes that the net warming observed to date is roughly as big as that expected from non-CO₂ gases only. This is because CO₂ warming is offset by climate-cooling aerosols emitted with fossil fuel burning and because at that time non-CO₂ gases, taken together, were responsible for roughly 50% of the anthropogenic greenhouse gas warming.

In a paper published May 18, 2007, Hansen discussed the potential danger of "fast-feedback" effects causing ice sheet disintegration, based on paleoclimate data. George Monbiot reports "The IPCC predicts that sea levels could rise by as much as this century. Hansen’s paper argues that the slow melting of ice sheets the panel expects doesn’t fit the data. The geological record suggests that ice at the poles does not melt in a gradual and linear fashion, but flips suddenly from one state to another. When temperatures increased to 2–3°C (3.6–5.4°F) above today’s level 3.5 million years ago, sea levels rose not by 59 centimeters but by . The ice responded immediately to changes in temperature."

Hansen stresses the uncertainties around these predictions. "It is difficult to predict time of collapse in such a nonlinear problem ... An ice sheet response time of centuries seems probable, and we cannot rule out large changes on decadal time-scales once wide-scale surface melt is underway." He concludes that "present knowledge does not permit accurate specification of the dangerous level of human-made [greehouse gases]. However, it is much lower than has commonly been assumed. If we have not already passed the dangerous level, the energy infrastructure in place ensures that we will pass it within several decades."

Responsibility for climate change

Hansen notes that in determining responsibility for climate change, the effect of greenhouse gas emissions on climate is not determined by current emissions, but by accumulated emissions over the lifetime of greenhouse gases in the atmosphere. By this measure the U.K. is still the largest single cause of climate change, followed by the U.S. and Germany, even though its current emissions are surpassed by the Peoples Republic of China.

On public policy, Hansen is critical of what he sees as efforts to mislead the public on the issue of climate change. He points specifically to the Competitive Enterprise Institute's commercials with the tagline "carbon dioxide—they call it pollution, we call it life", and politicians who accept money from fossil fuel interests and then describe global warming as "a great hoax." He also says that changes needed to reduce global warming do not require hardship or reduction in the quality of life, but will also produce benefits such as cleaner air and water, and growth of high-tech industries. He was a critic of both the Clinton and George W. Bush Administrations' stances on climate change. Addressing the potential effects of climate change, Hansen has stated in an interview in January, 2009, "We cannot now afford to put off change any longer. We have to get on a new path within this new administration. We have only four years left for Obama to set an example to the rest of the world. America must take the lead."

Hansen has been particularly critical of the coal industry, stating that coal contributes the largest percentage of anthropogenic carbon dioxide into the atmosphere. He acknowledges that a molecule of carbon dioxide emitted from burning coal has the same effect as a molecule emitted from burning oil. The difference is where the fuel originally resides. He says that most oil comes from Russia and Saudi Arabia, and that no matter how fuel-efficient automobiles become, the oil will eventually be burned and the emitted. In a 2007 testimony before the Iowa Utilities Board, he stated that the United States has a large reservoir of coal, which makes it a resource that can be controlled through action by U.S. politicians, unlike oil which is controlled by other countries. He has called for phasing out coal power completely by the year 2030.

During his testimony before the Iowa Utilities Board in 2007, Hansen likened coal trains to "death trains" and asserted that these would be "no less gruesome than if they were boxcars headed to crematoria, loaded with uncountable irreplaceable species." In response, the National Mining Association stated that his comparison "trivialized the suffering of millions" and "undermined his credibility." Citing the reactions of "several people" and "three of his scientific colleagues" as his primary motivation, Hansen stated that he certainly did not mean to trivialize suffering by the families who lost relatives in the Holocaust and then apologized saying he regretted that his words caused pain to some readers.

Hansen in his 2009 open letter to President Obama advocates a "Moratorium and phase-out of coal plants that do not capture and store CO₂". In his first book ''Storms of My Grandchildren'', similarly, Hansen discusses his ''Declaration of Stewardship'' the first principle of which requires "a moratorium on coal-fired power plants that do not capture and sequester carbon dioxide". Hansen also has spoken against cap and trade, instead advocating what he believes would be a progressive carbon tax at source carbon as oil, gas or coal, with a 100% dividend returned to citizens in equal shares

Honors and awards

Hansen was elected to the National Academy of Sciences in 1996 for his "development of pioneering radiative transfer models and studies of planetary atmospheres; development of simplified and three-dimensional global climate models; explication of climate forcing mechanisms; analysis of current climate trends from observational data; and projections of anthropogenic impacts on the global climate system." In 2001, he received the 7th Annual Heinz Award in the Environment (endowed with US$250,000) for his research on global warming, and was listed as one of Time Magazine's 100 Most Influential People in 2006. Also in 2006, the American Association for the Advancement of Science (AAAS) selected James Hansen to receive their Award for Scientific Freedom and Responsibility "for his courageous and steadfast advocacy in support of scientists' responsibilities to communicate their scientific opinions and findings openly and honestly on matters of public importance."

In 2007, Hansen shared the US $1 million Dan David Prize for "achievements having an outstanding scientific, technological, cultural or social impact on our world". In 2008, he received the PNC Bank Common Wealth Award of Distinguished Service for his "outstanding achievements" in science. At the end of 2008, Hansen was named by EarthSky Communications and a panel of 600 scientist-advisors as the ''Scientist Communicator of the Year'', citing him as an "outspoken authority on climate change" who had "best communicated with the public about vital science issues or concepts during 2008."

In 2009, Hansen was awarded the 2009 Carl-Gustaf Rossby Research Medal, the highest honor bestowed by the American Meteorological Society, for his "outstanding contributions to climate modeling, understanding climate change forcings and sensitivity, and for clear communication of climate science in the public arena."

Hansen won the 2010 Sophie Prize, set up in 1997 by Norwegian Jostein Gaarder, the author of the 1991 best-selling novel and teenagers' guide to philosophy "Sophie's World", for his " key role for the development of our understanding of human-induced climate change."

Controversies

Allegations of censorship

Hansen has stated that NASA administrators have tried to influence his public statements about the causes of climate change. Hansen said that NASA public relations staff were ordered to review his public statements and interviews after a December 2005 lecture at the American Geophysical Union in San Francisco. NASA responded that its policies are similar to those of any other federal agency in requiring employees to coordinate all statements with the public affairs office without exception. Two years after Hansen and other agency employees described a pattern of distortion and suppression of climate science by political appointees, the agency’s inspector general found that the NASA Office of Public Affairs had mischaracterized the science of climate change intended for the public.

Hansen has also appeared on ''60 Minutes'' stating that the George W. Bush White House edited climate-related press releases reported by federal agencies to make global warming seem less threatening. He also stated that he was unable to speak freely without the backlash of other government officials, and that he has not experienced that level of restrictions on communicating with the public during his career.

Trials for fossil fuel chiefs

In 2008 interviews with ''ABC News'', ''The Guardian'', and in a separate op-ed, Hansen has called for putting fossil fuel company executives, including the CEOs of ExxonMobil and Peabody Coal, on trial for "high crimes against humanity and nature", on the grounds that these and other fossil-fuel companies had actively spread doubt and misinformation about global warming, in the same way that tobacco companies tried to hide the link between smoking and cancer.

Arrests

On June 23, 2009, James Hansen, along with 30 other protesters including actress Daryl Hannah, were arrested on misdemeanor charges of obstructing police and impeding traffic, during a protest against mountaintop removal mining in Raleigh County, West Virginia. The protesters intended to enter the property of Massey Energy Company, but were blocked by a crowd of several hundred coal miners and supporters. Hansen said that mountaintop removal for coal mining "[provides] only a small fraction of our energy" and "should be abolished." Hansen called on President Barack Obama to abolish mountaintop coal mining.

Hansen and about 100 other people were arrested in September 2010 in front of the White House in Washington, DC. The group was seeking a ban on mountaintop removal or surface mining.

Hansen and 142 other activists were arrested in August 2011, at another demonstration in front of the White House. Hansen urged President Obama to reject the Keystone pipeline extension, intended to carry more synthetic crude oil from Canada's Athabasca Oil Sands to US markets.

Critics of Hansen

Andrew Freedman, an environmental journalist and columnist at the ''Washington Post'', believes the American Meteorological Society erred in giving Hansen its 2009 Carl-Gustaf Rossby Research Medal: "By citing his 'clear communication of climate science in the public arena,' they may have actually sanctioned his political advocacy. Such advocacy... threatens to paint the AMS as having a political agenda too." Other AMS members have also criticized the award.

Physicist Freeman Dyson is critical of Hansen's climate-change activism. "The person who is really responsible for this overestimate of global warming is Jim Hansen. He consistently exaggerates all the dangers... Hansen has turned his science into ideology.” Dyson "doesn’t know what he’s talking about", Hansen responded. "He should first do his homework." Dyson stated in an interview that the argument with Hansen was exaggerated by the New York Times, stating that he and Hansen are "friends, but we don't agree on everything."

After Hansen's arrest in West Virginia, ''New York Times'' columnist Andrew Revkin wrote: "Dr. Hansen has pushed far beyond the boundaries of the conventional role of scientists, particularly government scientists, in the environmental policy debate." In 2009, Hansen advocated the participation of citizens at a March 2 protest at the Capitol Power Plant in Washington, D.C. Hansen stated, "We need to send a message to Congress and the president that we want them to take the actions that are needed to preserve climate for young people and future generations and all life on the planet".

''New Yorker'' journalist Elizabeth Kolbert believes Hansen is "increasingly isolated among climate activists." Eileen Claussen, president of the Pew Center on Global Climate Change, said that "I view Jim Hansen as heroic as a scientist.... But I wish he would stick to what he really knows. Because I don't think he has a realistic idea of what is politically possible..."

''New York Times'' climate columnist Christa Marshall asks if Hansen still matters in the ongoing climate debate, noting that he "has irked many longtime supporters with his scathing attacks against President Obama's plan for a cap-and-trade system." "The right wing loves what he's doing," said Joseph Romm, a senior fellow at the Center for American Progress, a think tank. Hansen said that he had to speak out, since few others could explain the links between politics and the climate models. "You just have to say what you think is right," he said.

References

Further reading

External links

James Hansen's page at Columbia University

James Hansen's page at the Goddard Institute for Space Studies

Category:1941 births Category:American physicists Category:American climatologists Category:Living people Category:Members of the United States National Academy of Sciences Category:People from Crawford County, Iowa Category:NASA personnel Category:Sustainability advocates Category:Science activism

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