Negative Leap Second in Consideration

Negative Leap Second in Consideration

A recent study found that the melting of polar ice, an accelerating trend driven primarily by human-caused climate change, has redistributed mass on Earth enough to cause the Earth to spin slower than normal. Less solid ice at the poles means more mass is distributed around the equator, affecting the planet’s angular velocity. A figure skater twirling on ice is a good example of this.

Because of a combination of factors, the Earth has begun to spin faster in recent decades. This temporary trend prompted scientists to consider subtracting a single “negative leap second” from clocks worldwide as soon as 2026. However, the melting polar ice has delayed that possibility by about 3 years according to the recent study. If timekeeping organizations do eventually decide to add a negative leap second, the adjustment could disrupt computer networks.

Evan Bush, NBC News

Reforestation Creates Warming Hole in Eastern U.S.

Despite climate change cranking up the heat across the U.S., several eastern states have stayed curiously cool. Researchers think that successful reforestation is partly responsible. In the late 18th century, settlers cleared vast swaths of trees for farmland and timber. By the 20th century, some forests that had existed for thousands of years only had 10% of trees remaining. Land clearing slowed by the early 1900s and croplands were abandoned as people moved into growing cities, which allowed trees to begin to regrow. That regeneration, along with purposeful replanting, allowed millions of acres of forest to make a comeback during the 20th century.

As forests regenerated, the study found that air temperatures on the hottest days were up to 1.8F cooler in reforested areas than areas without forest. The surface temperature of the tree canopy was even milder, reduced by 1.8F to 3.6F annually compared to non-forested land. The cooling effect was most pronounced midday in the summer, lowering surface temperatures by up to 9F.

Jude Coleman, Scientific American

Heat Waves Last Longer, Spike Hotter, and Hurt More People

Since 1979, global heat waves are moving 20% more slowly, meaning people stay hot longer, according to a recent study. Heat waves are also happening 67% more often. The highest temperatures in the heat waves are warmer than 40 years ago and the area under a heat dome is larger. From 1979 to 1983, the average global heat wave would last 8 days. By 2016 to 2020, the average heat wave lasted up to 12 days.

Eurasia was hit especially hard with longer lasting heat waves, while heat waves slowed down the most in Africa. North America and Australia saw the biggest increases in overall magnitude of heat waves. The study found that atmospheric waves that move weather systems along, such as the jet stream, are weakening, so they are not moving heat waves along as quickly.

Seth Borenstein, Associated Press

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