A new Climate Central report, CLIMATE PILE-UP: Global Warming’s Compounding Dangers, offers in-depth insight and data, down to the city level.
How A Green New Deal Gone Global Could Affect The Climate Where You Live
Dozens of House Democrats have sponsored a resolution supporting a “green new deal,” endorsing the ambitious goal of eliminating net U.S. greenhouse gas emissions by 2030. Such a feat, which would be extremely difficult to pull off, would require rapid and wholesale changes across many major economic sectors, from energy production, to transportation, to agriculture and land use.
Widespread talk of such aggressive climate action is new in U.S. politics, and there’s no way to say whether a green new deal, if embraced and pursued by Americans, would spur or coincide with similar actions worldwide. (The U.S. has released more than a quarter of the greenhouse gas pollution currently in the atmosphere, and now it directly releases 15 percent of it each year.)
But the concept of dramatic reductions isn’t new to science. Scientists have repeatedly analyzed the impacts of various levels of emissions, including comparisons between strong reductions and continued emissions growth. A low-emissions scenario that climate scientists call RCP 2.6 involves getting global emissions to zero around 2070 — forty years after the target date named in the green new deal resolution. The extra time may make this scenario more plausible, but considering its global scope, it may be just as ambitious. At the other end of the spectrum, scientists also project future impacts under a high-emissions scenario that they call RCP 8.5.
The Consequences of Our Energy Choices
In its most recent comprehensive assessment, synthesized in 2014, the Intergovernmental Panel on Climate Change (IPCC) concluded that even the low levels of pollution released under RCP 2.6 could push global average temperatures up by about 1°C, or about 1.8°F, above 1986 to 2005 levels by the end of the century, with sea levels rising about another 1.3 feet.
Those impacts would be over and above the effects of climate change that have already occurred, further damaging the economy and public health. Global average temperatures have risen by about 1°C/1.8°F since the second half of the nineteenth century, and climate change has already bolstered heatwaves, droughts, coastal flooding and other hazards. The consequences for Americans have been wide-ranging. In 2015 alone, for instance, drought cost California’s agriculture sector $1.8 billion. Climate change intensified the rainfall of 2017’s Hurricane Harvey — a storm that caused some $125 billion in damages — by about 15 percent. And climate change has worsened wildfires in California. Last year, the Camp Fire destroyed more than 18,000 buildings and led to the deaths of more than 80 people.
“Broad threat to humanity from cumulative climate hazards intensified by greenhouse gas emissions,” a paper published in the journal Nature Climate Change by a group of researchers from the University of Hawai‘i and elsewhere, examined how human systems are vulnerable to climate-driven hazards, and how climate change is going to make those hazards worse. The paper identified 467 distinct impacts driven by 11 climate-linked hazards, including extreme heat, flooding, rising sea levels, storms, and changing ocean conditions.
Scientists have already documented all of those impacts — from livestock deaths during heatwaves in the Great Plains to the blackout in the Northeast after Hurricane Sandy. (A complete list of impacts, and the corresponding evidence, appears at impactsofclimatechange.info.) Many of these hazards interact to produce compounding threats. Sea level rise aggravates the impact from coastal storms, for instance, which cause flooding through heavy rain and by pushing storm surges inland. And when a heat wave strikes during a drought, demand for water rises when it’s already in short supply.
The paper showed that even a drastically-reduced, low-emissions future would worsen those hazards overall. But that outcome would be far more manageable than the changes brought about by a high-pollution future. Under RCP 8.5, temperatures are projected to climb by an additional 4°C/7.2°F by 2100, with seas rising by almost an additional 2.5 feet, according to the IPCC.
The paper incorporated data from hundreds of studies previously published worldwide. It graded 11 distinct climate hazards at locations around the world on a uniform, summable scale, scoring each hazard’s severity on a grade from -1 to 1. Under this system, a score of 1 represents the worst possible increase in severity in a given year relative to 1955 levels. Adding up the scores for all 11 hazards produced a cumulative impact score for each location, revealing the number of major hazards that location can expect in a given year. (In some locations, some hazards, such as drought, were projected to become less severe over time, due to more rain and snow in those locations.)
What A Global Green New Deal Could Mean for Your City
To examine the potential effects on residents of individual cities across the U.S. from an immediate and global reduction in greenhouse gas pollution, Climate Central worked with Camilo Mora, the Nature Climate Change paper’s lead author, and honed in on data for 244 cities across the United States.
The results show that unchecked emissions could put some parts of the country at risk of the equivalent of almost three major and concurrent climate hazards by 2050. Those compounding hazards would likely strain communities’ abilities to respond and cope. Immediate and aggressive global measures to curb warming would reduce projected threats by half at some locations in 2050, such as Baltimore, Maryland. Deep cuts to warming pollution would make an even starker difference at the end of the century.
The chart at the top of this bulletin shows how your local hazards would change by 2050 under very low and very high pollution scenarios. Charts for each city cover the top five impact areas. For information on all projected impacts in each city, download the data by clicking here. And to explore other climate impacts in your area, explore our media library.
*For more information: explore CLIMATE PILE-UP, Climate Central’s new research brief expanding this report’s information for cities across the United States.