Global Warming is a Terrible Danger for Humanity

by Mary

"In my more than three decades in the government I've never witnessed such restrictions on the ability of scientists to communicate with the public."

James Hansen

James Hansen is the country's premier Global Climate change scientist. Since the 1970s he has been at the forefront of the studying global climate change and has provided his expert opinion to every administration since then. Dr. Hansen believes that the world is in serious trouble -- so much trouble that he refuses to remain silent even when the Bush administration orders him to be so.

Tonight he was interviewed on 60 Minutes about why he was insisting on speaking out when the Bush administration has made it clear his talking to the public was unwelcome. Although James Hansen is an extremely well-known scientist, he was not allowed to talk with 60 Minutes without having a government minder sitting in the room. To my mind this shows what a threat the Bush administration believes him to be because now it is on the public record that they feel that he cannot be interviewed without someone watching what he is saying. Of course, this is because what Dr Hansen has to say is quite upsetting to the Bush corporate backers.

Dr. Hansen believes that we must slow down and reverse our carbon emissions within this decade or it will be too late to stop the worst of the consequences from global warming. In fact, he believes if we let things go on as they have been, by the end of the century humans will be living in a world that is totally different than mankind has ever known. Dr. Hansen has decided that he cannot be silent because if he doesn't say something he will not be fulfilling the NASA mission which is to understand and protect the earth.

As he wrote last month, what we are seeing right now shows that the problem is much graver than he and other scientists originally realized.

This new satellite data is a remarkable advance. We are seeing for the first time the detailed behavior of the ice streams that are draining the Greenland ice sheet. They show that Greenland seems to be losing at least 200 cubic kilometers of ice a year. It is different from even two years ago, when people still said the ice sheet was in balance.

Hundreds of cubic kilometers sounds like a lot of ice. But this is just the beginning. Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid. The issue is how close we are getting to that tipping point. The summer of 2005 broke all records for melting in Greenland. So we may be on the edge.

Our understanding of what is going on is very new. Today's forecasts of sea-level rise use climate models of the ice sheets that say they can only disintegrate over a thousand years or more. But we can now see that the models are almost worthless. They treat the ice sheets like a single block of ice that will slowly melt. But what is happening is much more dynamic.

Once the ice starts to melt at the surface, it forms lakes that empty down crevasses to the bottom of the ice. You get rivers of water underneath the ice. And the ice slides towards the ocean.

Our NASA scientists have measured this in Greenland. And once these ice streams start moving, their influence stretches right to the interior of the ice sheet. Building an ice sheet takes a long time, because it is limited by snowfall. But destroying it can be explosively rapid.

How fast can this go? Right now, I think our best measure is what happened in the past. We know that, for instance, 14,000 years ago sea levels rose by 20m in 400 years - that is five meters in a century. This was towards the end of the last ice age, so there was more ice around. But, on the other hand, temperatures were not warming as fast as today.

How far can it go? The last time the world was three degrees warmer than today - which is what we expect later this century - sea levels were 25m higher. So that is what we can look forward to if we don't act soon.None of the current climate and ice models predict this. But I prefer the evidence from the Earth's history and my own eyes. I think sea-level rise is going to be the big issue soon, more even than warming itself.

It's hard to say what the world will be like if this happens. It would be another planet. You could imagine great armadas of icebergs breaking off Greenland and melting as they float south. And, of course, huge areas being flooded.

How long have we got? We have to stabilize emissions of carbon dioxide within a decade, or temperatures will warm by more than one degree. That will be warmer than it has been for half a million years, and many things could become unstoppable. If we are to stop that, we cannot wait for new technologies like capturing emissions from burning coal. We have to act with what we have. This decade, that means focusing on energy efficiency and renewable sources of energy that do not burn carbon. We don't have much time left.

What's clear is we have no more time to waste. And we can't wait until Bush is out of office to get moving. The wholesale evacuation of New Orleans is a small harbinger of what we will see along all our coasts. 30 meters is more than 95 feet and many places like Portland, Oregon have sizable areas with elevations significantly lower than that. (In downtown Portland, the US Bank Tower is based at an elevation of 34 feet.) Manhattan would be gone as would much of Florida.

We know what the problem is. And we know what we need to do to fix it. Now we need to take action. If you want to know what you can do as an individual, you can start here. And we must make sure that the politicians are aware we expect them to do their part too.

[Updated 3/20/2006: Slight edits to the penultimate paragraph for greater clarity.]