Jerry Potter spends a lot of time looking back so fellow climate scientists can see the future more clearly.

Jerry is part of a group at NASA Goddard Space Flight Center that is studying weather and climate from past decades. The Climate Model Data Services Group collects weather data from the past to see if climate models generated from that information line up with the documented climate over the same time period.

“It’s really good for predicting things like the large-scale features of the atmosphere, like big high- and low-pressure systems,” says Jerry, a senior project scientist with the group.  “It’s not as good for predicting rainfall.”
Jerry began studying climate more than 40 years ago, long before the phrase “climate change” was a household term. He studied climatology at UCLA, where he earned his bachelor’s, master’s and Ph.D. degrees.  A paper he co-authored in 1989 on clouds is considered a seminal work in the field. He was deputy director of the Program for Climate Model Diagnosis and Intercomparison at Lawrence Livermore National Lab when he retired in 2005. Jerry was also a contributing scientist to the Intergovernmental Panel on Climate Change work that earned a Nobel Peace Prize in 2007. “Everybody I know worked on it,” he says with characteristic humility. “It’s not that big a deal. When we got it, they got us pizza.”

Retirement launched a new phase in his career.  Jerry now works five days a week as a contractor with NASA and UC Davis.

“It seemed like nobody cared what I thought when I was working,” he says with a laugh. “Now I’m the old man with years of experience in climate studies and everyone wants to know what I think.”
Jerry, 71, moved to Benicia in 1982 with his wife, Judy. They raised their two daughters here.

What have scientists learned about climate in the past decade? It’s an evolutionary thing. There are very few major discoveries; we understand things very gradually. What’s happening now is we’ve gotten bigger computers and can run models at a higher resolution. We get better predictions with higher resolution.
There are still some things that haven’t changed. There are still things we don’t understand. I gave a paper at an American Meteorological Society meeting in January about a wave in the upper atmosphere that we’re not sure what it is. When there were heat waves in 2003 in Europe and in 2010 in Russia, the atmosphere had a high-pressure system and you could see a wave in the upper atmosphere.
It occurs every five years or so and we don’t know if it’s real or not. It looks like this wave has been going around the Earth for the past 20 years, and it seems to cause heat waves but we don’t know what it is.

We know that there is this wave in the upper atmosphere when there are heat waves in Northern Europe and Russia and across Asia. You can see it over North America in the summer, but it’s not as far south as Texas so it isn’t associated with the 2011 heat wave there. But we don’t know if this wave is random or not.

It started about 1998 to 2000, which is also when we started having increasing occurrences of heat waves. Is the wave (in the upper atmosphere) related to climate change? We don’t know.

What do the models tell us now about climate change? The models all agree that the Earth will continue to warm because of the effect of greenhouse gases. It’s just our bad luck that the carbon dioxide molecule absorbs heat.  

We can measure the increase in carbon dioxide and have been able to do so for decades.  A chemist by the name of Arrhenius—he’s Swedish—predicted this about 120 years ago.

I don’t think anyone denies that the earth is warming. Glaciers are melting; everyone can see what’s happening. It’s the cause that some question. But scientists have looked at this and there is no other explanation other than human behavior. We’ve eliminated all other possible causes.

Do you follow political discussions about climate change? Not a huge amount. I’d rather read the science part than the politics part.

What are some of the expected effects of climate change in the coming years? There will be variability, but in general over the next 30 years, the Earth has to adjust for extra carbon dioxide in the atmosphere.  But how that increased carbon dioxide affects rain and clouds – that’s what we’re trying to figure out.

We’re not sure droughts and heat waves are related to climate change. You can’t blame the current drought on climate change. We’ve had droughts in the past that lasted for years. But scientific papers say manmade climate change may have exacerbated the drought.

Can we do something to reverse the increase in greenhouse gases? It is possible to reduce our emissions to the point where carbon dioxide will be reduced.  Whether we will or not is something else. It’s a long-time recovery even if we stop now.

But if we go on with business as usual, which is what most people expect to happen, the Earth will warm several degrees. The models say that will bring sea level rise, increasing variability in weather and climate, more droughts and more floods and more heat waves. Most models predict there will be more extreme conditions. Events like 100-year floods are already happening more frequently than they should.

What do you do for NASA? The NASA job is trying to get weather data from the past in a form so people can study it. Every day, groups around the world that get data use it to forecast the weather. So we said, “Let’s put in the data from the past and see if our models can predict what the weather was.”  We’re working with a group in Japan, one in Europe and three in the United States.
It’s very useful because you test your climate models and see how well we’re doing. It’s called reanalysis. It’s not my job to write papers any more, but I am working on a paper to announce this project. It’s called the Collaborative Reanalysis Technical Environment—CREATE.

What work are you doing for UC Davis? I’m helping diagnose this new climate model that’s being developed at all the national labs under a contract with the Department of Energy.  I’m helping to develop the tools to assess the model, and I’m working at Livermore (Lawrence Livermore National Lab) as a subcontractor from UC Davis. The project at Livermore is called ACME, which stands for Accelerated Climate Modeling for Energy.

What can people do to reduce greenhouse gasses? Use less energy. Gas is cheap again and people are buying big cars and trucks again. Put solar panels on your house. People shouldn’t give up even if gas and electricity are cheap. Everybody can help make a difference.

What is a reliable source for info on the climate and climate change? The guy I like is Gavin Schmidt (director of the NASA Goddard Institute for Space Studies).  He has a web site— All the big names in climate are there.

What do you like to do to relax? I like to listen to classical music. I like to bicycle. I like to walk. I like seeing my kids.

What’s next for you? I’m going to be a grandfather this fall!
I’m going to work a few more years. My dad worked until he was 78. I have a good friend who retired at 75. I think that’s when I’ll retire.  But what do you do when you retire? I have to do something to feel like I’m contributing to society.     

Editor’s note:   Jerry Potter was first interviewed by Benicia Magazine in the June 2007 issue about his work as a climate scientist.  The 1989 article mentioned above was published in Science and is listed by the National Science Digital Library as one of 20 key articles published on climate change between 1824 and 1995. Jerry is the only person to be featured in Benicia Magazine’s Q&A for a second time.