It feels hot for a reason, and not just in the United States. Last month’s global average land surface temperature was the fourth warmest on record. And July is doing its best to outdo June. According to the National Oceanic and Atmospheric Administration, 49 states — all except Delaware — have had record highs in the past three weeks. In Washington, a heat wave sweeping the East Coast is pushing temperatures into triple digits.
However, while suffering Washingtonians might be forgiven for regarding this summer as an aberration, they would be wrong. Globally, June was the 316th month in a row that had a higher temperature than the 20th century average. So, while it is indeed much hotter than it used to be, we may be witnessing a new normal in heat and other extreme weather. This month’s temperature records may not stand for long.
“Hundred year” weather events happen only once every 100 years.
Hundred-year weather events no longer live up to their name. In 2005, for instance, a devastating “once a century” drought hit the Amazon, only to be followed by another in 2010. Globally, previously rare weather events have been occurring with startling frequency. Consider the massive floods that inundated a fifth of Pakistan last year and submerged eastern Australiaand America’s heartlandthis year. It’s time for meteorologists to come up with a new, more accurate term.
Of course, what scientists actually mean by “one in 100 years” is not that a major flood, drought or hurricane will strike a given place only once a century, but rather that there is a 1 percentchance of such an event in any given year. Either way, the fact that what were once considered hundred-year events seem to be happening more often is consistent with climate models projecting that rising global average temperatures will lead to more frequent and severe extreme weather.
Extreme droughts and extreme floods can’t both be due to climate change.
It seems counterintuitive that climate change could be responsible for both withering droughts and devastating floods. Yet it can. Scientists have found that climate change can trigger periods of intense rainfall followed by long spells of dry weather. This combination of severe rainstorms and droughts, in turn, can lead to more flooding, landslides, soil erosion and other disasters. There are signs in some places that this may already be underway.
For example, from 1951 to 2000, heavy monsoons in India became more frequent and intense, while more moderate rains happened less often. Similarly, in China, severe droughts this spring were followed by massive flooding, which has killed nearly 200 people and caused more than 1.5 million to be evacuated.