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In the Firing Line of a Hot Debate

Kevin Trenberth

Kevin Trenberth was at the centre of controversy when his emails were leaked and taken out of context by climate change deniers.

By Stephen Luntz

Kevin Trenberth is finding the signal of global warming in extreme weather events while dodging the abuse of those who wish to silence him.

Kevin Trenberth once thought he would become a seismologist. If he had it would have made for a quieter life. Instead he applied his skills in fluid dynamics to meteorology, but found his words twisted to reverse their meaning in newspapers across the world and his inbox full of hate mail.

Trenberth did so well at high school maths in New Zealand that he was allowed to skip first year university and go straight to the second year of a science degree. He considers this an important factor in his choice of science over engineering, despite what he calls “the lack of a clear career path”. With honours in mechanics and fluid dynamics from the University of Canterbury, his postgraduate studies at Massachusetts Institute of Technology (MIT) involved “creating a very early climate model to study the phenomenon of sudden stratospheric warming”.

Sudden stratospheric warming events occur when there is a major breakdown in the polar westerlies, with warm air rising from the troposphere into the stratosphere. Most occur in the Arctic, but one has been observed in the south. The phenomenon was a puzzle at the time and Trenberth says he “made inroads” into understanding it.

Trenberth made his name in scientific circles with his work on the southern oscillation. “This was first discovered in the 1890s with variations in the Indian Monsoon, ” he says. Some attention was paid until the 1920s, but it was only in the 1950s that the connection to El Niño warm oceans was brought in. “I wrote a paper on it,” Trenberth says. “We realised El Niño and the oscillation were connected, one being an atmospheric effect and one being oceanic.” The name ENSO has since been coined to unite the two, and entered the popular vocabulary as the explanation for the droughts that periodically grip eastern Australia while floods occur in other parts of the world.

“New Zealand is particularly affected by ENSO,” says Trenberth, explaining why he caught onto the importance of the cycle before most colleagues. He had returned to his country of birth to work at the Meteorological Service after graduating from MIT, but moved to the University of Illinois and then the US National Center for Atmospheric Research where he is now based.

Trenberth played an important role in the writing of the second, third and fourth Intergovernmental Panel on Climate Change (IPCC) reports, in each case working in a different capacity. But it was his work on the fourth report, collaborating with Dr Phil Jones of the University of East Anglia, that brought him unwanted fame. When hackers broke into the University’s email accounts messages to and from Trenberth were among those illegally released. In the lead-up to the Copenhagen climate summit, sections were lifted out of context to make it seem that Trenberth questioned whether humans really were warming the climate.

“One piece was interpreted as saying there was no global warming, when what I was actually saying was that we had inadequate studies,” says Trenberth. Since then the pressure on climate scientists has grown. “I got a huge number of vitriolic messages. Now if you publish a paper in Science or Nature you immediately get a number of nasty emails.” Climate science is now probably the only area of science where death threats are routine, with some researchers moved to more secure offices as a result.

“Some scientists have responded by retreating to their ivory towers, and a couple have become very distressed. Others have become aggressive and wanted to fight back,” Trenberth says. “I understand it is a political campaign and don’t take it personally, so I am able to take it more equably than some others. I do try to do more public outreach, however, and make myself more available to the media.” He considers it problematic that scientists are generally not rewarded for time spent explaining their research to the public.

Trenberth was interviewed while in Australia for a meeting on the effects of global warming on the hydrological cycle. Trenberth took the opportunity to give a public lecture on the role of climate change in extreme weather events, which has become his main area of research.

While many scientists take the view that we cannot attribute any single disaster to global warming, Trenberth thinks they are looking at the problem the wrong way. “Tests are done using the 95% significance level, saying we need to be 95% confident that something is not a chance event. But if we turn this around and say, ‘Let’s assume a human influence, and prove that there is not,’ you can’t prove there is no human factor in the extreme events either.”

Trenberth speaks with great authority in this matter. His publication record puts him among the top 20 geophysicists in the world. His h-index, a measure of the impact of an author’s scientific papers, is 64, possibly the highest in his field and well above the average for members of the National Academy of Sciences, almost 10% of whose members have won Nobel Prizes.

Trenberth believes that asking, “Is this caused by climate change?” is the wrong question. “There is always human influence. The real question is how large is the human influence. Was it large enough to make a difference? It is clear we are outside the range of natural variability.” For examples, Trenberth points to the record heat leading up to Victoria’s Black Saturday bushfires, followed a year later by a Russian heatwave that killed 50,000 people and distorted global wheat prices, contributing to the Arab Spring uprising.

Trenberth says that as people are already dying from climatic events with a human signature we cannot avoid many of the consequences of what we are doing to the planet. “We can live with these for another 30 years or so, but around 2050 the climate will be sufficiently different that a lot of crops will no longer be able to be grown, we will see major food and water shortages. Mitigation can push this further into the future so we have more time to adapt. Slowing down the problem has pay-offs but they mostly happen 30 years from now.”

Responses, in Trenberth’s opinion, need to start with a price on carbon emissions and the abolition of “absolutely absurd” subsidies for fossil fuels. He has put photovoltaic panels on his home in Colorado and better insulated the house. “I drive a small car, take the bus to the airport and try to set an example, but all these things only make a difference if a lot of people do them. In Colorado, incentives for solar panels help but these little bits don’t solve the problem.”

As frustrating as the lack of political will to change may be, Trenberth hopes that a more aware public will respond when disasters strike. “It’s a really tough question whether climate change will cause more El Niños. The thing that is apparent is that floods and droughts are becoming more extreme,” he says.

Trenberth’s work is helping us predict how rainfall and evaporation patterns will change, giving options to prepare for those willing to take them. Until now, not many have. However, in the aftermath of disasters like Queensland’s recent floods – the second in 2 years – the message “we told you so” may finally start to resonate.