Climate change and extreme weather

By Art Piltch

Reader Contributor

Climate models predict that the more the earth heats up, the more likely we are to experience extreme weather. With the earth warming around 10C (1.80F) since 1900, and the 17 hottest years on record occurring since 1998, we are already seeing record- breaking natural disasters becoming regular occurrences.

Extreme heat waves are becoming more common worldwide, as the rising average global temperature, tips the odds more in their favor. The World Weather Attribution Program found that the heat wave that hit Europe in the summer of 2003, and killed some 70,000 people, is 10 times as likely to happen as it was just a decade ago. Lethal heat waves have even occurred in the spring. One that struck India in May 2015 killed more than 2,500 people, and melted asphalt roads.

Global warming is expected to increase precipitation in humid areas and decrease precipitation in arid areas. A pattern of atmospheric circulation over the tropics, called the “Hadley cell”, is responsible for maintaining humidity over the equatorial tropics, while bringing hot-dry air to the subtropics. With global warming, the Hadley cell appears to be expanding away from the equator, bringing a more arid climate to regions including parts of Africa and Australia, and the American Southwest. The worst drought to ever affect Australia occurred between the years 2003 to 2012, and many regions are still in significant drought. The worst drought in decades across southern and eastern Africa, coupled with record high temperatures, is putting 36 million people at risk of hunger. Recent U.S. droughts have been the most expansive in decades. For example, in 2011, Texas experienced its driest 12 months ever. At the peak of the 2012 drought, an astounding 81 percent of the contiguous United States was under at least abnormally dry conditions. In California, the four-year period between fall 2011 and fall 2015 was the driest since record keeping began in 1895.

Climate change is also producing conditions ripe for wildfires. The first six months of 2015 were the warmest first six months of any year over much of Oregon and Washington since record keeping began in 1895. These record-warm temperatures observed during the winter and spring, coupled with below-average precipitation, led to an exceptionally poor snowpack throughout the winter and spring. The 2015 fire season in the Pacific Northwest was the most severe in modern history. In Washington, there are now five times as many large fires burning in a typical year as there were in the 1970s; in Oregon there are nearly seven times as many. Taking into account wildfires in California and the Rocky Mountains, more than 10 million acres burned across the western U.S. in 2015. The average number of large fires burning each year on Forest Service land has increased at least tenfold in the Northern Rocky Mountain states of Wyoming, Idaho and Montana. Climate change is also decimating forests by contributing to population explosions of insect pests, and through water stress.

The amount of rain produced by tropical storms is influenced by the increased evaporation from warmer oceans, and warmer air which holds more moisture. Record to near-record warm ocean temperatures in waters off the southeastern U.S. in 2016 led to extreme amounts of rainfall. In March, a 200 year rainfall event brought 15-20 inches of rain to parts of Louisiana and Texas, killing five people and causing $1.5 billion in damage. Then in August, a 1,000-year storm brought more than 20 inches of rain to Louisiana, causing 13 deaths and $10-15 billion in damage. Then in October, Hurricane Matthew devastated Haiti, killing over 500 people, and caused a storm surge, which brought water levels that were the highest ever observed, along portions of the coasts of Northern Florida, Georgia and North Carolina. It dumped one-in-1,000 year rains in some areas of South Carolina and North Carolina. Matthew killed 49 people in the U.S., with damage estimated at up to $10 billion. The storm surge would have been much less if sea levels hadn’t risen eight inches over the last century. In 2017, the “pineapple express,” an atmospheric river that carries moist air from the tropical pacific around Hawaii to California has caused extreme rainfall, with flooding around the state, including damage to the spillway at the Oroville dam, leading to the evacuation of 188,000 people. The severity of this type of event is projected to increase with global warming. This is particularly worrying, since the Army Corps of Engineers categorizes 833 dams in California alone to have “high hazard potential.”

Extreme rainfall events also occurred in other areas of the world. Torrential monsoon rains in eastern China, in the summer of 2016, destroyed 145,000 homes and killed more than 500 people, with economic losses that reached $28 billion. Historic flooding inundated parts of France and Germany in late May and early June 2016, after days of record-breaking rainfall. These events are considered 80-90 percent more likely than they were in the past.

If we are already seeing these impacts of only a 1.80F average global warming, what does the future hold in store? Projections of the probability of extreme weather depend on how much more the level of greenhouse gas increases. For example, according to a 2015 NASA study, there is an 80 percent likelihood of a three-decades-long megadrought in the Southwest and Central Plains in the latter half of this century, if greenhouse gas emissions continue to increase along current trajectories. That’s much longer than the dust bowl drought of the 30s. The effects of such a drought would lead to food and water shortages unlike anything we’ve experienced so far in U.S. history. In the most optimistic scenario, where the whole planet transitions away from fossil fuel as fast as we can, we might limit average temperature rise to 3-40F. That would require limiting the use of fossil fuels to around 20 percent of current reserves, and leaving the rest in the ground. If we exceed that amount of warming, aside from increasing extreme weather, we also run the risk of reaching a “tipping point”, where climate change will get much, much worse, and keep accelerating, even if we completely stop using fossil fuels.