The Science for Determining Climate-Change Damage Is Unsettled
Unsettled is key word for the climate sciences.
The Science for Determining Climate-Change Damage Is Unsettled
Tying individual weather events to global warming remains a challenge, and research on the causes of recent flooding in Pakistan yields mixed results
Flooding in Pakistan was cited in an agreement to set up a fund for nations harmed by the effects of climate change.
PHOTO: FIDA HUSSAIN/AGENCE FRANCE-PRESSE/GETTY IMAGES
By Eric Niiler, and Stacy Meichtry, Nov. 26, 2022 5:30 am ET
Delegates at the recent COP27 climate summit in Egypt agreed to set up a fund to compensate poorer nations harmed by the effects of climate change. But figuring out the extent to which climate change causes the harm, and to which countries, is testing the limits of a new field known as attribution science.
The United Nations loss-and-damage fund aims to transfer money from wealthy nations to poor nations deemed especially vulnerable to the effects of climate change. Those eligible to receive funding include countries in Africa and Asia as well as island nations in the Pacific and the Caribbean. Some analysts expect the annual financing needs of the countries to reach $290 billion to $580 billion by 2030.
Questions remain about how the fund will operate and whether it can act quickly to help affected countries. As officials work out the details, scientific uncertainty over the attribution of human-induced climate change to individual weather disasters risks deterring wealthy nations from contributing funds.
Weather events including Hurricane Ian, which struck Florida, raise questions on the impact of climate change.
PHOTO: SEAN RAYFORD/GETTY IMAGES
Attribution science is still evolving, according to Richard Spinrad, administrator of the National Oceanic and Atmospheric Administration. He said his agency’s focus is on understanding the effects of climate change—such as the duration and number of tropical storms or the extent of sea-level rise—rather than pinpointing the causes of specific weather events.
“I do not see NOAA getting involved in providing some attribution index for that typhoon or that hurricane,” Dr. Spinrad said.
Some weather events are made worse by increased atmospheric and ocean temperatures and rising sea levels, according to the Intergovernmental Panel on Climate Change. But it has been unable to attribute specific weather events to climate change.
Lisa Graumlich, a professor of environmental and forest sciences at the University of Washington, said scientists now face the challenge of developing tools to assess loss and damage and determine whether climate change is to blame for individual weather events.
“I think we’re in some very undefined territory right now,” said Dr. Graumlich, who is the president-elect of the American Geophysical Union.
In approving the fund, COP27 delegates cited devastating floods in Pakistan that killed an estimated 1,700 people and caused more than $30 billion in damages. Pakistan’s delegation led the effort to get a loss and damage agreement on the COP27 agenda and pushed for its adoption.
NOAA’s Richard Spinrad says his agency isn’t focused on pinpointing the causes of specific weather events.
PHOTO: CHANDAN KHANNA/AGENCE FRANCE-PRESSE/GETTY IMAGES
A recent study of the floods yielded mixed results. The research, which hasn’t been published in a journal, showed that total rainfall this year in the affected region was more than seven times higher than the historical average and that climate change had intensified rainfall in the region during a week-long period in late August. In addition, computer models showed that rainfall during that period was 75% more intense as a result of climate change than it would have been in the absence of climate change.
But the scientists didn’t detect a role for climate change throughout the two-month monsoon season. Other factors, including strong La Niña ocean-temperature conditions in the Pacific region, might explain the 50% surge in rainfall intensity during the season, according to Friederike Otto, lead author of the study and a senior lecturer in climate science at Imperial College, London.
“Pakistan was not straightforward,” she said.
The researchers also noted gaps in their analysis. “There are large uncertainties in these estimates due to the high variability in rainfall in the region, and observed changes can have a variety of drivers, including, but not limited to, climate change,” they said in the study’s summary.
The impact of the floods was made worse by the settlements and farms in floodplains, an outdated river-management system, high levels of poverty and Pakistan’s ongoing political and economic instability, according to the research.
“Every time we do a study like this, we learn more of what combination of variables that you can measure actually leads to the impacts,” Dr. Otto said. “And we don’t have a very good understanding of that yet.”
One approach used by scientists attempting to link climate change to weather events involves measuring the impact of slow-onset events such as the rise in sea levels, which in combination with more intense storms can inundate river deltas.
In Bangladesh, coastal erosion from sea-level rise is driving thousands of migrants a day to the capital, Dhaka, said Saleemul Huq, director of the Dhaka-based International Centre for Climate Change and Development.
“There’s a very strong climate-change signal that is forcing them to be displaced,” said Dr. Huq, who has written several reports for the U.N. on adaptation to climate change.
Metrics showing the loss of livelihood among people displaced by climate change are available but haven’t been adopted by the U.N., he said.
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The insurance industry has been battered by damage claims from weather events, but it has been unable to develop a computer program or actuarial table capable of determining the extent to which a storm, flood or drought can be blamed on climate change, according to Ernst Rauch, chief climate scientist at the German reinsurance firm Munich Re.
“Science cannot provide a sort of legal proof which can be taken to court in the legal systems which we have in Western societies,” Dr. Rauch said. Many factors go into calculating loss and damage from weather events, he said, including population growth in coastal areas, a nation’s gross domestic product and existing infrastructure aimed at limiting flood damage.
“Climate attribution science will improve over time,” Dr. Rauch said. “But in 10 years or so will it be clear and will it be narrowed down to one single number and say, ‘Well, 25% is climate change?’ I don’t believe it.”
Write to Eric Niiler at eric.niiler@wsj.com and Stacy Meichtry at Stacy.Meichtry@wsj.com