Fletcher in the News

Professor Moomaw Discusses Leaked UN Report and Climate Change

Here & Now


In a leaked climate report, the Intergovernmental Panel on Climate Change (IPCC) — a United Nations scientific body that makes definitive assessments on climate change — has determined with 95 percent certainty that humans are responsible for global warming.

The report also increased its estimate for sea level rise, as a result of the warming planet.

The final report is due to come out in September. A draft was leaked over the weekend.


It's HERE AND NOW. And it was not supposed to be released until next month, but the leaks are coming out about a big United Nations report on climate change. It says human activity is almost certainly the cause of climate change and that rising temperatures are to blame for warming ocean waters, the melting of Arctic ice and sea level rise. The report says that sea levels worldwide could rise by three feet by the year 2100. To help us understand what we know about the report and its significance, we're joined by William Moomaw, a professor of international environmental policy at The Fletcher School at Tufts University. He was a lead author on previous climate change reports, and he's with us now from Williamstown, Massachusetts. Professor Moomaw, welcome.

WILLIAM MOOMAW: Thank you for having me.

HOBSON: Well, so the leaked draft of this U.N. report says that it is now 95 percent certain that climate change is caused by human activity. The last report in 2007 said it was just 90 percent certain that this was being caused by humans. How big of a difference is that? Does it matter?

MOOMAW: Well, the scientists are never willing to say something as absolutely certain, so they always put some kind of probability on it. And I remember when the early report said it is possible that humans are causing climate change, and then it went to it is as likely as not and then - and so on and so forth. It's been strengthened over time. And in 2000 it was decided to put some kind of a numerical number on it. So the difference between 90 and 95 percent may not seem like much, but to scientists saying 95 percent puts it within a range that they feel comfortable as saying, yup, it's happening.

HOBSON: Yet the leaked draft does backtrack from the previous report as far as the projected minimum temperature the planet could warm if carbon dioxide levels double. The previous report used a minimum of 3.6 degrees Fahrenheit. The new draft says 2.7 degrees. What's the difference there?

MOOMAW: It's a small difference, and in fact the 2.7 degree number was the number that was used for all the reports prior to the 2007 report. So it's basically going back to where we were before. Remember that the upper range, the upper estimate is still the same, eight degree Fahrenheit. So that hasn't changed.

Listen to the full interview

Follow us on Twitter