Scientists have not yet proven cause and effect. But climate researcher Peter Stott says extreme weather events are on the rise — as climate models have long predicted
From the brutal heat wave in Russia that may have killed 15,000 people, to the devastating floods in Pakistan that have displaced millions more, extreme weather events and the climatic processes that lead to them have been in the news all summer long.
Many climate activists are drawing clear cause and effect links between these events and global warming. For example, here’s a headline from the Climateprogress blog: “Climate experts agree: global warming caused unprecedented Russian heat wave”
But is it really quite so clear cut? To what degree is climate change leading to increases worldwide in extreme weather events?And what further research is needed in this area?
To get some answers, I interviewed Peter Stott for “How on Earth,” the weekly science and environment radio program on KGNU FM radio here in Boulder. Stott is head of climate monitoring and attribution at the United Kingdom’s Met Office. He is in Colorado this week for the first full session of a scientific group called the Attribution of Climate-related Events. ACE consists of scientists from the National Center for Atmospheric Research, the UK Met Office, and the National Oceanic and Atmospheric Administration.
Click here to listen to the interview at KGNU. (Scan forward to about 14 minutes and 20 seconds into the broadcast to access the beginning of the interview segment.)
And for excerpts and additional perspective on these issues, continue reading . . .
Despite the claims of bloggers and climate activists, Stott as well as other experts say that it is impossible to say that a particular extreme weather event like the Pakistani floods or the Russian heat wave were “caused” by global warming. They offer more nuanced, if still sobering, assessments.
From the interview:
I think . . . some people are too easily jumping from the very clear evidence that climate is changing, and that we’ve seen systematic changes in our climate system over the last few decades, to saying that particular individual extreme weather events are therefore due to climate change and therefore will become more frequent in the future . . .
The example with the current terrible situation in Pakistan is a very good case in point. Although our understanding of the climate system does tell us, and the observations do tell us, that there have been increases in extreme rainfall events, we don’t know about the particular circumstances in Pakistan, and the particular weather situation there, whether that is the sort of thing that will become more frequent or not. And, therefore, [we don't know how to] respond to such a situation in terms of the longer-term adaptation response, for example.
What we would like to do with further research is really nail down whether what we’re looking at has more to do with variability of the climate system — are we seeing a very rare meteorological event? . . . which may not be the sort of thing that becomes more common in the future — or whether we are seeing something that really is the sort of thing that a particular locality can expect to see more of in the future.
I pointed out that recent analyses from both NASA and NOAA pegged January through July as the hottest such period on record. Seventeen countries had record temperatures this summer. And in addition to the floods, Pakistan had Asia’s hottest day ever recorded. In May, one city reached 53.5 degrees Celsius, which is 128 degrees Fahrenheit. On the other hand, such extremes are a natural part of the climate system. “So as a scientist, what can you say with fair confidence now about this summer’s events?,” I asked Stott.
To start off with, you highlighted the global temperature. And that’s right, globally temperatures are very warm, historically. We’ve shown . . . that the first decade of the 21st century was the warmest decade on record. And that is very clear.
Alongside this global warming has come some some very consistent consequences that climate models have long predicted . . . including the fact that the atmosphere has gotten more humid, and including the fact that there are broad scale changes in the precipitation patterns over the surface of the Earth. And also alongside with that has come a clear trend that’s been observed in the number of extreme temperatures that have been measured, and also the fact that there have been more heavy rainfall events.
So all of this adds up to a consistent picture. And it really means that the chances that we’ve got it wrong, that the scientific consensus is wrong about that this, that there isn’t a major human influence on climate — the chances that that’s the case seems to keep reducing as we get more and more data.
In other words, it is true that what we saw this summer fits the pattern of observed increases in certain kinds of extreme weather events. Moreover, these increases are consistent with our understanding of the physics of climate change. And they have long been predicted by computer models.
But cause and effect is something else. The whole point of the ACE workshop that Stott is attending is to figure out how scientists can do a better job of attributing the specific causes of these events.
We’re interested in being able to respond better to the question that always gets asked when we have extreme weather events . . . which is, what has caused them both meteorologically and whether they are linked to climate change or not.
This is scientifically both an important area and also I think a relatively new area . . . Although there has been a lot of work done on the very large scale global climate changes, in terms of the temperatures and the very large scale rainfall patterns . . . there has been relatively little work done looking much more closely at whether particular extreme events, whether they be the floods in Pakistan or heat waves in Russia or even the very cold winters that parts of the U.S. and the U.K. have had recently — whether these are linked to just natural variability . . . or whether these are the sorts of the things that we would expect more of in the future because of climate change.
In a recent New York Times article, Gavin Schmidt, a climate scientist with NASA, summed up the issue succinctly: “If you ask me as a person, do I think the Russian heat wave has to do with climate change, the answer is yes. If you ask me as a scientist whether I have proved it, the answer is no — at least not yet.”