Saturday, September 10, 2011

Extreme weather: is there a link with global warming?

As Britons sit at the end of a dull summer bracing ourselves for high winds created by the tail end of Hurricane Katia, it is natural to question whether extreme the weather may be connected to our driving habits global warming.

I wrote a year ago about extreme weather events. Time for an update.
It is impossible to say at the moment whether a single particular event is down to global warming (though we can say that all extreme events are consistent with global warming theory).

We have to look for trends.

This is what we're finding:

Thanks to Meehl/NACR
In a recent report, Jerry Meehl of the National Center for Atmospheric Research finds that extreme weather events are becoming more frequent.  He also finds that record highs are trending ahead of record lows:
Meehl et al, 2009

Hurricanes must increase as sea surface temperatures increase.

And the record suggests that hurricanes are indeed increasing:

These figures and other  interesting facts on this US Global Change Research Program page.

So a picture is emerging. This is not proof: regular readers of this blog (peace be upon them) will know that science does not do proof. But a picture is emerging. 

Strange things are happening to the weather, as predicted by climate science.

The Norwegian Cicero Institute commissioned a report in 2002, titled Climate change and extreme weather events: Is there a connection? In it we find these words:

It’s hard to escape the perception that extreme weather events are increasing... However, extensive press coverage on extreme weather events may be prejudicing our perception of the issue.

Which is true.

Natural phenomena that might explain a possible increase in extreme weather events do exist. For example, El Niño and La Niña are known to precipitate extreme weather events. 

This is also true. 

However, warm El Nino events are on an increasing trend, again, consistent with climate science:

Their conclusion:
No clear consensus exists linking the frequency and intensity of extreme weather events to changes in climate patterns, but it would be reckless to not expect that climate change will have some impact on extreme weather events.

That was in 2002. Nine years later, it seems, unfortunately, that we are slowly moving closer to a consensus.

[update 27 Aug 2012] 
here is a pretty good match between hurricane intensity and the Atlantic Multidecadal Oscillation (a measure of temperature of the Atlantic)
Data courtesy of NOAA and Landsea et al. 2010.
[update 5/9/13
Here is a link to US extreme weather index. Clear evidence of a recent increase: ]


Anonymous said...

DocRichard said...

Thanks for that link, Anon.
It points to the difficulties in attributing specific weather events to climate change. We have to look for trends, and apply mathematical analyses.