“We are now able to put a number on the deaths caused by climate change in a heat wave,” said lead author Daniel Mitchell of the University of Oxford. “This has never been done before. Previous studies have attributed changes in heat waves to climate change, or related increased heat stress to human deaths, but none have combined the two.”
The study’s U.S. and U.K researchers calculated that, during a Europe-wide heat wave in summer 2003, 506 of 735 deaths in Paris and 64 of 315 deaths in London were due to a heat wave worsened by anthropogenic climate change. They reached that conclusion after putting the results of several thousand runs of two climate model simulations of the 2003 heat wave into a health impact assessment of death rates.
By comparing two scenarios—one reflecting the climate of 2003 without human influences and one reflecting all known climatic forces contributing to the 2003 heat wave—the researchers determined how climate change had affected that summer’s temperatures.
The study, reports Carbon Brief, analyzes a direct impact measure—mortality—rather than an indirect one—temperature. It links mortalities to climate and introduces another level of uncertainty, especially when long and reliable health datasets are not available for use in analyses.
Nevertheless, reports ClimateWire, the study demonstrates that losses can be directly linked to climate change and thus its framework can be used to assign costs of “loss and damage” and to improve planning and adaptation (subscription).
“It is often difficult to understand the implications of a planet that is one degree warmer than preindustrial levels in the global average, but we are now at the stage where we can identify the cost to our health of man-made global warming,” Mitchell said. “This research reveals that in two cities alone hundreds of deaths can be attributed to much higher temperatures resulting from human-induced climate change.”
Last week at a meeting held by the French government to study Paris Agreement-related actions to reduce health risks linked to climate change, the World Health Organization said that change is likely to kill 250,000 additional people each year by 2030—primarily through malaria, diarrhea, heat stress, and malnutrition. Children, women, older people, and the poor will be most affected.
Climate Change and Cloud Cover
A new study in the journal Nature suggests there’s evidence of climate change in satellite cloud records. By comparing satellite data from 1983 to 2009 to climate models, the authors found that the clouds forming most often are not low-lying reflective ones that cool the planet. Instead, cloud patterns were in line with what scientists would expect to see in climate models—an increase in greenhouse gases associated with human activity over the study period.
“Cloud changes most consistently predicted by global climate models are currently occurring in nature,” the authors write. “As cloud tops rise, their greenhouse effect becomes stronger.”
Clouds have both an Earth-cooling effect by reflecting solar radiation back to space and an Earth-warming effect by restricting the planet’s thermal infrared radiation.
“Even if there is no change in the overall coverage of clouds on the earth, clouds closer to the pole reflect less solar radiation because there is less solar radiation coming in closer to the pole,” said lead author Joel Norris of the Scripps Institution of Oceanography.
In Science magazine, Norris noted one caveat: during the study period, two major volcanic eruptions cooled and then warmed the climate, producing cloud patterns similar to those produced by greenhouse gas-related warming.
Draft Proposes Extension of California Cap-and-Trade Program
The California Air Resources Board released a draft plan to extend the state’s cap-and-trade program beyond 2020, when it is set to expire. The program—one of the first economy-wide programs put in place—aims to reduce greenhouse gas emissions by creating a fixed number of permits, called allowances, to emit a single ton; compliance entities and other market participants can buy and sell allowances, thereby enabling the market to determine the lowest-cost compliance path.
The draft plan calls to extend the program another decade and to reach emissions levels 40 percent below 1990 levels. It would include preliminary caps through 2050 “to signal the long-term trajectory of the program to inform investment decisions.”
No board vote is scheduled on the proposal until March 2017. A state appeals court is considering a challenge from the California Chamber of Commerce, which contends that the pollution-credit program is an illegal tax, not a fee.
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.