Are the IPCC predictions too optimistic?

Question

As George Monbiot writes, James Hansen's research suggests that this is the case.

"The IPCC predicts that sea levels could rise by as much as 59cm 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 degrees above today’s level 3.5 million years ago, sea levels rose not by 59 centimetres but by 25 metres. The ice responded immediately to changes in temperature."

http://www.monbiot.com/archives/2007/07/03/a-sudden-change-of-state/#more-1072

Hansen's paper available here:

http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_2.pdf

If Hansen is correct, our tendency not to react until a problem's consequences are very tangible may be our downfall.

Answer 1

Absolutely.

""The drafting of reports by the world’s pre-eminent group of climate scientists is an odd process. For many months scientists contributing to the Intergovernmental Panel on Climate Change tussle over the evidence. Nothing gets published unless it achieves consensus. This means that the panel’s reports are extremely conservative – even timid. It also means that they are as trustworthy as a scientific document can be."

George Monbiot

Then there is the editing of the scientists done by the policy people. While the scientists are pretty successful in limiting those edits, the ones that do occur invariably make the reports more optimistic (ie slightly reduce the problem of global warming and the portion attributed to man).

Answer 2

The IPCC predicts that sea levels could rise by as much as 59cm 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 degrees above today’s level 3.5 million years ago, sea levels rose not by 59 centimetres but by 25 metres. The ice responded immediately to changes in temperature."

http://www.monbiot.com/archives/2007/07/...

Hansen's paper available here:

Answer 3

Maybe is the best answer.

All predictions have a margin of error, at least if you are using science.

If all the assumptions the IPPC used are correct, their result would occur. But there is a low probability of that occurring.

It could be worse, it could be better. Until we can create models that can predict correctly past behavior, any attempt to predict future behavior will have a large margin of error. That's just the nature of scientific models.

Personally though, I live 125 feet above sea level, so I'm not concerned either way.

Answer 4

Welcome to science by "consensus"...


...live by the sword, die by the sword. Who do you think demanded that the predictions not overreach the already tenuous computer modeling data? At least give the IPCC credit for trying to remain consistent in methodology.

But this is rich, an Alarmist ready to jettison the "consensus"...

Answer 5

Hansen has even stated he pushes the worst case scenario to instill the most fear and get the most attention for his cause.