News•September 27, 2013

Claudia Tebaldi Discusses the IPCC Process and Findings

By Climate Central

The Intergovernmental Panel on Climate Change released part of its Fifth Assessment Report on Friday. It contains a wealth of information on climate change and its impacts around the globe. Climate Central Senior Scientist Claudia Tebaldi is a lead author on the newly released section and discusses some of the highlights and the process of drafting the massive report in the video and transcript below.

Q: How much feedback did scientists get during the draft phase of the report?

Tebaldi: We received more than 50,000 review comments on this draft. And we responded to each and every one of those in a traceable way.

Q: Has the process for putting the report together changed between the 2007 report and this one?

Tebaldi: At least, comparing the last report that came out in 2007 to this report that just came out, the process hasn’t changed in any radical way. We were very careful to base our summary and our assessment on peer-reviewed literature – nothing gray, nothing that hadn’t undergone a substantial assessment by the scientific community.

Q: What are the key takeaways from this report?

Tebaldi: The Earth is warming, that we are responsible for most of it, and we are becoming more and more certain that we are responsible for most of it. And that we will keep on changing this climate in a more severe ways if we keep on emitting greenhouse gases through our fossil fuel consumption as we have been doing.

Q: Are you surprised by these findings?

Tebaldi: We haven’t found anything that has made us change our minds in a radical way about what has happened, what’s going to happen, and what’s the cause of it.

Q: The new report says scientists are 95 percent certain humans are causing the climate to change. That’s up from 90 percent in the 2007 report. What does that mean?

Tebaldi: It’s a marginal, if you want, increment. But it’s an increment in the direction that, unfortunately, means we are responsible and it’s more and more certain we are responsible. And it’s more and more certain that things are just going to get worse if we don’t do anything about it.

Q: How can scientists trace the carbon dioxide to human activities?

Tebaldi: We see that it’s organic, but we also see that it’s an organic matter that is very, very, very old. So it doesn’t come, for example, from burning plants now that were alive just yesterday or a year ago. It comes from burning plants that were alive millions of years ago and now are oil or coal or natural gas.

Q: How do you explain the slowdown in the rate of warming?

Tebaldi: We know that climate can have these moments of cooling for 10 or 15 years. If we come back in another 15 years and we’re still in a cooling period, then we will start questioning our understanding much more deeply. But for now, 10 or 15 years are still very much consistent with our understanding of how our climate works and how human-caused warming works.

Q: What about other climate change indicators? Are they still shifting?

Tebaldi: If I were an oceanographer, for example, I would say that I would be offended because the atmosphere warming is just one aspect of global warming. If we look at the ocean temperature, they have increased steadily during these last 10 or 12 years. If we look at the melting of glaciers, they have kept on melting at even greater rates than before. If we look at sea-level rise, it has been increasing more and more – even during the last 10 or 12 years. So there are a lot of aspects to climate change that are not just atmosphere warming. And those are sill out there, still working against us.

Q: What are one or two specific findings in the report?

Tebaldi: The report says very explicitly that when it comes to heat extremes we have seen those changing very coherently across regions over the world in the last decades.

Q: What are some of the other findings?

Tebaldi: We know that increased warming brings about much more frequent and intense and severe heat extremes. Precipitation events are going to be much more frequent. And I have to say, I’ve just survived the flood here in Boulder, and that is something that really concerns me now more than just two weeks ago. To think about going through that more frequently is not something that I want to think about right now.

Q: Can we expect more extremes in the future?

Tebaldi: Definitely for heat and precipitation extremes we expect to see more of those in the future.

Q:There’s a lot of attention on the polar regions of the Earth. What does the report say about those areas, particularly sea ice?

Tebaldi: When it comes to Arctic sea ice and Antarctic sea ice, they are very different processes at play. For the Arctic, it’s really just, or for the most part, the simple idea is that as we warm the atmosphere and we warm the ocean, Arctic sea ice is melting. At the Antarctic, the temperatures are really much, much colder. So, they are still warming, but not warming enough to just melt the ice as easily as it melts in the Arctic. So in the Antarctic it’s more about the effects of wind that break up the ice and more the ice in certain directions. And by doing that, they open up water that is easier to ice over. So there are much more complex dynamics there.

Q: Is global warming reversible?

Tebaldi: Climate change is considered irreversible mainly because of the long lifetime of carbon dioxide in the atmosphere. Once we emit carbon dioxide, and once it stays in the atmosphere, it stays there for hundreds and hundreds and hundreds of years.

Q: Is there another way to do a comprehensive climate report?

Tebaldi: It would be very difficult to find a way to come up with a synthesis that is reliable, that is rigorous, that is as transparent, as the IPCC does.

Q: What did you learn from being a part of the process?

Tebaldi: What I was surprised by was the level of effort and commitment of my colleagues, and by the rigor of the process. That was beyond my expectations, even if I knew going in there that it was going to be a big effort and a big time commitment.

Q: What’s the goal of report?

Tebaldi: The goal of the report is to be used by policymakers, by government, to inform themselves about the science of climate change and inform their decisions.