Scientists have warned that even a few degrees rise in global temperatures can lead to increasingly severe storms. Now an international team of climate scientists has linked man-made climate change to historic flooding that hit the south of England in the winter of 2013–2014. It’s the first time a peer-reviewed research paper has connected climate change to a specific flooding event.
In an article published in Nature Climate Change, the team said that their climate model simulations showed that anthropogenic warming not only increased the amount of moisture the atmosphere can hold but also caused a small but significant increase in the number of January days with westerly flow, both of which increased extreme precipitation. The authors explained that climate change “amplified” the violent storms that led to the area’s wettest January in more than a century and that it has likely increased the number of properties at risk and raised the costs of a flooding event.
Based on more than 130,000 simulations of what the weather would have been like with and without human influence on the climate, the study finds that man-made greenhouse gas emissions have raised the possibility of extreme flooding by 43 percent.
“What was once a 1 in 100-year event in a world without climate change is now a 1 in 70-year event,” said study co-author Friederike Otto of Oxford University.
The study—which analyzed circulation in the atmosphere, the additional risk of rainfall, and swollen river flows and then calculated flood potential in the Thames River Basin—goes beyond previous attempts to connect climate change with specific weather events, tracing connections “all the way from the changes in the atmosphere to the impacts on the ground,” lead author Nathalie Shaller of Oxford University told Agency France Presse.
“This study highlights the fact that we need a better understanding of not just how and where climate change is warming the atmosphere, but also how it is changing patterns of wind and rain, in order to best prepare for extreme rainfall and floods,” said Ted Shepherd, a climate change expert at the University of Reading.
Long-Term Warming Not Unpredictable
Large sustained changes in global temperatures do not rise or fall erratically long term, suggesting the importance of changes in atmospheric circulation and the transfer of energy in balancing Earth’s temperature after a warming event. That’s according to a study published in the Journal of Climate by researchers at Duke University and the National Oceanic and Atmospheric Administration (NASA).
“The bottom line of the study is that the Earth is able to cool itself down after a natural warming event, like an El Nino,” said lead author Patrick Brown, a Duke Ph.D. student. “So then in order to have sustained warming for decades to centuries, you really do need these external drivers, like the increase in greenhouse gases.”
Using global climate models and NASA satellite observations from the last 15 years, the authors cite the Planck Response—the huge increase in infrared energy Earth emits as it warms—for the planet’s capacity to restore the stability of global temperatures. Other important factors, say the authors, are energy transport from the tropic Pacific to polar and continental locations and a net release of energy across cooler regions during unforced, natural warming events.
Studies: East Coast Should Prepare for Warming-Related Sea-Level Rise
Two studies published this week point to regional differences in climate-change-related sea-level rise, specifically, to greater impacts for the U.S. East Coast. A study in Nature Geoscience by researchers at the National Oceanic and Atmospheric Administration (NOAA) finds that “Atlantic coastal areas may be particularly vulnerable to near-future sea-level rise from present-day high greenhouse gas emission rates.” A second study in Proceedings of the National Academy of Sciences finds a higher-than-expected contribution by thermal expansion to sea-level rise from 2002 through 2014—expansion that led to a rapid rise for the East Coast and a slight temporary drop for the Pacific Coast.
Using a climate change model that simulates the ocean, the atmosphere and carbon cycling, the NOAA study examined sea-level rise in the Atlantic, versus that in the Pacific, under multiple global carbon emissions scenarios. It found that if greenhouse gas emissions rates remained consistent with today’s rates, seal levels in the Atlantic would rise much faster than in the Pacific. The difference owes to the Atlantic’s greater “overturning” ocean circulation that connects waters off New York with those off Antarctica. If this circulation slows due to climate change, the researchers concluded that less cold water will dive to ocean depths, warmer water will pool below the surface, and overall warmth will increase. This warm water expands, causing the study’s expected sea level rise, which will have regional variations based on topography and other factors.
The study in the Proceedings of the National Academy of Sciences put the contribution of thermal expansion to rising sea levels at 50 percent. Based largely on satellite readings of changes in water volumes and masses in seas, the study suggests that tallies of the effects of ocean warming on sea-level rise using autonomous seafaring instruments have underestimated thermal expansion.
The Climate Post offers a rundown of the week in climate and energy news. It is produced each Thursday by Duke University’s Nicholas Institute for Environmental Policy Solutions.