Events such as hurricanes and wildfires are too often blamed on our slowly warming, slightly wetter planet
Two weeks ago, President Donald Trump greeted the cold snap that was gripping much of the U.S. by tweeting, “Perhaps we could use a little bit of that good old Global Warming.” He was criticized for confusing weather with climate. But he’s hardly alone in making this mistake, as we have seen in coverage of the most destructive weather-related events of 2017.
The past year was filled with bad weather news, much of it tragic, with whole communities even now still struggling to recover. Hurricane Harvey hit Texas, and Hurricane Irma struck Florida and Puerto Rico after devastating other Caribbean islands. Wildfires torched the dry expanses of Napa and Ventura counties in California, and Australia experienced severe heat waves.
It has become routine for the media, politicians and activists to link such awful events with climate change. The basic claim is that the accumulation of greenhouse gases in the atmosphere is causing more extreme weather of every kind—more droughts, floods and hurricanes. This comes in addition to concerns that a rise in global temperatures will have potentially dire effects in the long term on polar ice and sea levels.
By looking at the world as a whole, however, and at long-term trends (climate) rather than at short-term events (weather), we can better test the claims that 2017 was an unusual weather year and that weather is getting more extreme as the world warms. This global and long-term view also puts other possible threats from climate change in perspective.
While the U.S. witnessed record damages in 2017, the rest of the world was actually hit by far fewer natural disasters than usual. On average, the globe suffers some 325 catastrophic natural disasters a year, but last year (through November) they were down to around 250, according to the Centre for Research on the Epidemiology of Disasters at the University of Leuven in Belgium. A third fewer people were killed by climate-related hazards, according to the Centre’s International Disaster Database.
As for major weather events and the most prominent indicators of long-term climate trends, here is a rough scorecard for 2017:
Temperature: The past three years have set global records for high temperatures, partly thanks to the recurring warm-water El Niño cycle in the Pacific Ocean. Moreover, temperatures have been at historic highs since 2000, with 16 of the 17 warmest years on record. But average surface temperatures have dropped by a half degree Celsius since the El Niño peak in 2016, according to the UK’s Met Office, and are now almost back to pre-El Niño levels.
Global average surface temperatures (1997-2017). Source: UK Met Office HadCrut4
Though temperatures have increased, the rise is not accelerating and has fallen short of the most authoritative projections. In 1990, the first assessment report of the U.N.’s Intergovernmental Panel on Climate Change predicted that temperatures would rise at the rate of 0.3 degree Celsius per decade, equivalent to 3 degrees Celsius (or 5.4 degrees Fahrenheit) a century. In fact, temperatures have risen since 1990 at between 0.121 and 0.198 degrees Celsius per decade, depending on which of the best data sets is used—that is, at a third to two-thirds of the rate projected by the IPCC.
Hurricanes: In August, Harvey made landfall near Corpus Christi as a Category 4 storm, ending a record 12-year period without a major U.S. hurricanes. Last year’s Atlantic hurricane season was particularly hyperactive, ranking as the seventh most intense Atlantic season since records began in 1851.
But cyclones (as hurricanes are known elsewhere) are found in all three tropical oceans, and globally the Accumulated Cyclone Energy index—which measures the combined intensity and duration of these storms—is currently running 20% below its long-term average. In fact, the index for 2017 was less than half of normal cyclone activity for the Southern Hemisphere.
Fires and droughts: More than 9,000 wildfires burned some 1.4 million acres across California this year. But the number of wildfires in California has actually been declining for 40 years, according to UCLA’s Jon Keeley, a leading researcher on the subject.
A review published in 2016 by Britain’s Royal Society documented that the global area burned by wildfires has also declined in recent decades.
As for drought, a comprehensive database published in 2014 in the journal Nature found that the proportion of the world suffering from abnormally low rainfall has slightly declined since the 1980s. […]
Floods: In 2017, California had its second wettest rainy season since record-keeping began more than a century ago, setting off massive floods. But a study published last year in the Journal of Hydrology by Glenn A. Hodgkins of the U.S. Geological Survey and colleagues concluded that the number of major floods in natural rivers across Europe and North America has not increased in 80 years. Globally, too, floods have decreased in recent years.