by Judith Curry
[I]n the past year, climate researchers in the United States and Britain have formed a loose coalition under the banner ‘ACE’ — Attribution of Climate-related Events — and have begun a series of coordinated studies designed to lay the foundations for a systematic weather-attribution programme.
Nature has just published a News Feature entitled “Climate and weather: Extreme measures.” Subtitle: Can violent hurricanes, floods, and droughts be pinned on climate change? Scientists are beginning to say yes.
When the weather gets weird, as happens a lot these days, one question inevitably arises from reporters, politicians and the general public alike: is this global warming?
The question was asked after last year’s catastrophic floods in Pakistan and record-breaking heat wave in Russia. It was asked again this year about the freakish tornado clusters in the southeastern United States and the devastating drought in Africa. And it was asked yet again this August as Hurricane Irene roared up the US East Coast.
For the most part, climate researchers have shied away from answering. Their mantra has been that science cannot attribute any particular drought or hurricane to climate change; the best it can do is project how the frequency of extreme weather events might change as the globe warms, through shifts in factors such as evaporation rates over the open ocean, water vapour and cloud formation, and atmospheric circulation.
Lately, however, that reluctance has started to fade. “My thinking has evolved,” says Gavin Schmidt, a climate modeller at the NASA Goddard Institute for Space Studies in New York.
Also in the past year, climate researchers in the United States and Britain have formed a loose coalition under the banner ‘ACE’ — Attribution of Climate-related Events — and have begun a series of coordinated studies designed to lay the foundations for a systematic weather-attribution programme. Ultimately, the group hopes to create an international system that could assess the changing climate’s influence on weather events almost as soon as they happen or even before they hit, with results being announced on the nightly weather reports.
“The idea is to look every month or so into the changing odds” associated with that influence, says Peter Stott, a climate scientist with the UK Met Office’s Hadley Centre in Exeter and a leader of the ACE group. Stott is writing a white paper laying out plans and requirements for a near-real-time attribution system, which he will present in October at the World Climate Research Programme conference in Denver, Colorado.
So the goal of the ACE group is to carry out ‘fractional attribution’ of extreme events, estimating how much each one was influenced by anthropogenic greenhouse warming and how much by natural cycles (see‘Climate shift’).
Although the basic approach seems straightforward, says Stott, fractional attribution is only as good as the climate models that drive it. “We still need to understand which types of weather events we can confidently attribute,” he says, “and those for which the models are not yet good enough.”
Such deficiencies in the models explain why many climate scientists remain sceptical of attribution efforts. “Scientifically unsound” is the assessment of Judith Curry, a climatologist at the Georgia Institute of Technology in Atlanta. Even converts such as Schmidt are cautious. “There is a lot of scope for doing a much better job,” he says.
The ACE group plans to address these shortcomings in next month’s white paper. As a first step, the group suggests that leading centres, such as NCAR and the Met Office, carry out fractional attribution assessments of notable weather extremes over the past 50 years, using large ensembles of coupled climate models and all available weather data. The lessons learned from these retrospective studies could then allow scientists to progress into routine attribution of recent weather, as well as climate-based forecasts of extreme weather.
It is not yet clear what such a plan would cost, or who would pay for it. Kevin Trenberth, a climate scientist with the NCAR, estimates that a few million dollars would be enough to coordinate an international service using facilities already in place at his institution, the Met Office and elsewhere. But going beyond this bare-bones effort — creating, for example, a free-standing attribution centre with monthly, seasonal and decadal forecasting capacities — would cost much more.
Nature also has an editorial on this, link [here].
JC comment: My quote “Scientifically unsound” succintly summarizes my opinion on this. My reasoning is described extensively in previous posts.
The rationale for ACE seems to be described by this statement:
But neither weather nor climate pays the slightest attention to what policy-makers are doing. And with events such as Hurricane Irene making themselves felt in politicians’ backyards, an attribution service might someday be seen as a good investment.
Never let a good disaster go to waste in terms of trying to play on people’s emotions to generate support for CO2 mitigation policies.
Fortunately, there seems to be little prospect for ACE in the short term:
Given that governments on both sides of the Atlantic are slashing their budgets wherever possible, Trenberth admits that the prospects for launching such a programme anytime soon seem remote.
I can save everyone tons of money on this. The NOAA group in Boulder is already doing an excellent job [website here]. They no longer refer to it as “attribution” but rather as “interpreting climate conditions.” They focus on past observations and weather patterns, and seasonal climate forecast products. Of course, it takes them days to weeks to do an analysis on a single extreme event, so you miss the maximum emotional impact of the analysis. With two more FTE NOAA employees devoted to this effort, they could study more storms and/or produce the assessment more quickly.
Clarification. People seem confused as to why I am praising the NOAA group, while I am not at all impressed by the proposed ACE effort. The NOAA group examines the historical data record, looks for past analogues, and interprets the extreme weather event in the context of the weather and climate dynamics. In the three examples of “Whats happening now”, they explained the Russian heatwave, the snowy winter, and the tornado outbreak in the context of natural weather and climate variability. By contrast, the ACE effort is focused on using climate models to assess the fraction of the event that might be attributed to global warming. It is the use of climate models for this exercise that I object to, which I explained in a previous post.