Storms such as the one shown above, which blew in off Lake Erie last November and dumped a year’s worth of snow in a week on western New York state, are in part linked to human-caused climate change, according to a newly released study by the U.S. National Oceanic and Atmospheric Administration (NOAA). But pinning down the cause of any single weather event-a specific heat wave, hurricane, or drought-is much more challenging, since extreme things could still happen without global warming.
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They found evidence of such influence in half those weather events, they reported. “The underlying processes that relate climate change to heat wave intensity and frequency are fairly straightforward to understand: if you increase the average temperature by even a modest amount, then it turns out that you dramatically increase the area under the extreme positive “tail” of the distribution”, Michael Mann, a climate scientist at Penn State who wasn’t involved in any of the new studies, said in an email.
The scientists, however, did not discern the influence of climate change in every event, nor did they see it playing a consistent role in certain types of events, like drought. Others, such as extreme rainfall in the United Kingdom last winter, showed no link at all.
The fact that human activities are affecting weather events across the globe requires little verification now.
The Argentinian heatwave of December 2013 was made five times more likely because of human-induced climate change.
Humans can influence weather events in other ways other than climate change, this year’s report finds.
What was the impetus for this report?
Generally speaking, temperature-related events were more closely aligned with climate change than precipitation-related events. For other events, like the drought in Brazil and flooding in the Canadian prairies, humans influenced the likelihood in other ways besides the greenhouse gases that continue to be emitted into the atmosphere.
Climate change has helped shift the odds of extreme heat.
We can’t blame climate change for everything.
Nor could an all-time record number of storms over the British Isles, extreme rains in Britain, Hurricane Gonzalo in Europe or drought in north-eastern Asia be attributed to climate change. One study showed a role in the southern Levant region of Syria, while another study, which looked more broadly at the Middle East, did not find a climate change influence.
The intense wildfire activity in California in 2014 was another extremely complex topic that researchers delved into, finding that while they couldn’t pick out any direct climate change signal in that year’s fires, warming is likely to exacerbate future fire risk.
“All that is unusual is not necessarily happening due to climate change”, he said.
Of the eight heat events examined-including ones in Argentina, Australia, South Korea, China and Europe-seven were clearly made more likely because of human-caused warming.
The report was edited by Herring, along with Martin P. Hoerling, NOAA’s Earth System Research Laboratory; James Kossin, NOAA’s National Centers for Environmental Information; Thomas Peterson, World Meteorological Organization’s Commission for Climatology and formerly with NOAA’s National Centers for Environmental Information; and Peter A. Stott, UK Met Office Hadley Centre.
A third study focused on the Horn of Africa, which includes parts of countries such as Kenya and Somalia that also face high food insecurity and political instability.
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“AMS is pleased to collaborate with NOAA on providing the public with an accessible, peer-reviewed basis for understanding our changing world”, said AMS Executive Director Keith Seitter. Two other drivers, central Pacific sea surface temperatures and atmospheric conditions in the North Atlantic, did not appear to be influenced by climate change.
