Climate

Hurricane Maria and Heat Wave Henrietta?
For decades, meteorologists have named hurricanes and ranked them according to severity. Naming and categorizing heat waves too could increase public awareness of the extreme weather events and their dangers, contends a newly formed group that includes public health and climate experts. Developing such a system is one of the first priorities of the international coalition, called the Extreme Heat Resilience Alliance.
Hurricanes get attention because they cause obvious physical damage, says Jennifer Marlon, a climate scientist at Yale University who is not involved in the alliance. Heat waves, however, have less visible effects, since the primary damage is to human health.
Heat waves kill more people in the United States than any other weather-related disaster (SN: 4/3/18). Data from the National Weather Service show that from 1986 to 2019, there were 4,257 deaths as a result of heat. By comparison, there were fewer deaths by floods (2,907), tornadoes (2,203) or hurricanes (1,405) over the same period.
What’s more, climate change is amplifying the dangers of heat waves by increasing the likelihood of high temperature events worldwide. Heat waves linked to climate change include the powerful event that scorched Europe during June 2019 (SN: 7/2/19) and sweltering heat in Siberia during the first half of 2020 (SN: 7/15/20).
Some populations are particularly vulnerable to health problems as a result of high heat, including people over 65 and those with chronic medical conditions, such as neurodegenerative diseases and diabetes. Historical racial discrimination also places minority communities at disproportionately higher risk, says Aaron Bernstein, a pediatrician at Boston Children’s Hospital and a member of the new alliance. Due to housing policies, communities of color are more likely to live in urban areas, heat islands which lack the green spaces that help cool down neighborhoods (SN: 3/27/09).
Aaron Bernstein, a pediatrician at Boston Children’s Hospital, says giving heat waves names and severity rankings may help save lives.John Wilcox for Coverage, a BCBS of MA news service
Part of the naming and ranking process will involve defining exactly what a heat wave is. No single definition currently exists. The National Weather Service issues an excessive heat warning when the maximum heat index — which reflects how hot it feels by taking humidity into account — is forecasted to exceed about 41° Celsius (105° Fahrenheit) for at least two days and nighttime air temperatures stay above roughly 24° C (75° F). The World Meteorological Organization and World Health Organization more broadly describe heat waves as periods of excessively hot weather that cause health problems.
Without a universally accepted definition of a heat wave, “we don’t have a common understanding of the threat we face,” Bernstein says. He has been studying the health effects of global environmental changes for nearly 20 years and is interim director of the Center for Climate, Health and the Global Environment at the Harvard T.H. Chan School of Public Health.
Defined categories for heat waves could help local officials better prepare to address potential health problems in the face of rising temperatures. And naming and categorizing heat waves could increase public awareness of the health risks posed by these silent killers.
“Naming [heat waves] will make something invisible more visible,” says climate communicator Susan Joy Hassol of Climate Communication, a project of the Aspen Global Change Institute, a nonprofit organization based in Colorado that’s not part of the new alliance. “It also makes it more real and concrete, rather than abstract.”
The alliance is in ongoing conversations with the National Oceanic and Atmospheric Administration, the World Meteorological Organization and other institutions to develop a standard naming and ranking practice.
“People know when a hurricane’s coming,” Hassol says. “It’s been named and it’s been categorized, and they’re taking steps to prepare. And that’s what we need people to do with heat waves.”

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To curb the spread of COVID-19, much of the globe hunkered down. That inactivity helped slow the spread of the virus and, as a side effect, kept some climate-warming gases out of the air.
New estimates based on people’s movements suggest that global greenhouse gas emissions fell roughly 10 to 30 percent, on average, during April 2020 as people and businesses reduced activity. But those massive drops, even in a scenario in which the pandemic lasts through 2021, won’t have much of a lasting effect on climate change, unless countries incorporate “green” policy measures in their economic recovery packages, researchers report August 7 in Nature Climate Change.
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“The fall in emissions we experienced during COVID-19 is temporary, and therefore it will do nothing to slow down climate change,” says Corinne Le Quéré, a climate scientist at the University of East Anglia in Norwich, England. But how governments respond could be “a turning point if they focus on a green recovery, helping to avoid severe impacts from climate change.” 
Carbon dioxide lingers in the atmosphere for a long time, making month-to-month changes in CO2 levels difficult to measure as they happen. Instead, the researchers looked at what drives some of those emissions — people’s movements. Using anonymized cell phone mobility data released by Google and Apple, Le Quéré and colleagues tracked changes in energy-consuming activities, like driving or shopping, to estimate changes in 10 greenhouse gases and air pollutants. 

“Mobility data have big advantages” for estimating short-term changes in emissions, says Jenny Stavrakou, a climate scientist at the Royal Belgian Institute for Space Aeronomy in Brussels who wasn’t involved in the study. Since those data are continuously updated, they can reveal daily changes in transportation emissions caused by lockdowns, she says. “It’s an innovative approach.”
Google’s mobility data revealed that 4 billion people reduced their travel by more than 50 percent in April alone. By adding more traditional emissions estimates to fill in gaps (SN: 5/19/20), the researchers analyzed emissions trends across 123 countries from February to June. The researchers found that the peak drop occurred in April, when globally averaged CO2 emissions and nitrogen oxides fell by roughly 30 percent from baseline, mostly due to reduced driving.
Fewer greenhouse gases should result in some cooling of the atmosphere, but the researchers found that effect will be largely offset by the roughly 20 percent fall in sulfur aerosols in April. These industrial emissions reflect sunlight and thus have a cooling effect. With fewer shading aerosols, more of the sun’s energy can heat the atmosphere, causing warming. On the whole, the stark drop in emissions in April alone will cool the globe a mere 0.01 degrees Celsius over the next five years, the study finds.
In the long-term, the massive, but temporary, shifts in behavior caused by COVID-19 won’t change our current warming trajectory. But large-scale economic recovery plans offer an opportunity to enact climate-friendly policies, such as invest in low-carbon technologies, that could avert the worst warming (SN: 11/26/19). That could help reach a goal of cutting total global greenhouse gas emissions by 52 percent by 2050, limiting warming to 1.5 degrees Celsius above preindustrial levels through 2050, the researchers say.

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The intense heat wave that gripped Siberia during the first half of 2020 would have been impossible without human-caused climate change, a new study finds. Researchers with the World Weather Attribution Network report that climate change made the prolonged heat in the region at least 600 times more likely — and possibly as much as 99,000 times more likely.
“We wouldn’t expect the natural world to generate [such a heat wave] in anything less than 800,000 years or so,” climate scientist Andrew Ciavarella of the U.K. Met Office in Exeter, England, said July 14 in a news conference. It’s “effectively impossible without human influence.”
The new study, posted online July 15, examined two aspects of the heat wave: the persistence and intensity of average temperatures across Siberia from January to June 2020; and daily maximum temperatures during June 2020 in the remote Siberian town of Verkhoyansk.

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Tiny Verkhoyansk made international headlines when it logged a record high temperature of 38° Celsius (100.4° Fahrenheit) on June 20 (SN: 6/23/20). The record was just one extreme amid a larger and longer event in the region that has led to a series of human and natural disasters (SN: 7/1/20). Those include wildfires across Siberia, the collapse of a fuel tank in the mining city of Norilsk due to sagging permafrost, and heat health effects (SN: 4/3/18).
Using observational data from Verkhoyansk and other Siberian weather stations, the researchers first assessed the rarity of the observed temperatures and determined temperature trends. Then they compared these observations with hundreds of climate simulations using different greenhouse gas warming scenarios. 

Had such a hot spell occurred in 1900 instead of 2020, it would have been at least 2 degrees cooler on average, the researchers found. In Verkhoyansk, climate change amped up June temperatures by at least 1 degree relative to 1900. And such heat waves are likely to become more common in the near future, the scientists found: By 2050, temperatures in Siberia could increase by between 2.5 degrees to as much as 7 degrees compared to the year 1900, the report finds. More

On June 20, a remote Siberian town called Verkhoyansk logged a temperature of 38° Celsius (100.4° Fahrenheit), likely setting a new high-temperature record for the Arctic Circle (SN: 6/23/20). But that new record didn’t occur in a vacuum: It’s part of a long-term trend of historically hot temperatures in Siberia linked to climate change, and […] More

The remote Siberian town of Verkhoyansk is known for its extreme cold: Winter temperatures often dip below –50° Celsius. But on June 20, temperatures in the town soared to a high of 38° C (100.4° Fahrenheit). If confirmed by the World Meteorological Association, that marks the hottest temperature ever recorded north of the Arctic Circle. […] More

Mangrove forests can only take so much. The famously resilient, salt-tolerant and twisty trees have so far managed to keep pace with rising sea levels, providing a valuable buffer to coastal communities against pounding storm surges. Now, researchers have found the forests’ limit.  Mangroves cannot survive in seas rising faster than about 7 millimeters per […] More

Tree StoryValerie TrouetJohns Hopkins Univ., $27 Once you look at trees through the eyes of a dendrochronologist, you never quite see the leafy wonders the same way again. Peel away the hard, rough bark and there is a living document, history recorded in rings of wood cells. Each tree ring pattern of growth is unique, […] More

Increasingly powerful tropical cyclones in the North Pacific Ocean may be fueling a powerful north-flowing ocean current, helping to boost the amount of heat it ferries to northern latitudes. By enhancing the speed of some ocean whirlpools called eddies, and suppressing the spin of others, the passing storms may be accelerating the heat-carrying Kuroshio Current […] More