Four charts that highlight this summer’s freakish temperatures

The Economist

Four charts that highlight this summer’s freakish temperatures

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To read more of The Economists data journalism visit our Graphic Detail page. THERE HAS been no shortage of alarming stories, with alarming charts, about the climate recently. Extreme weather is hitting several regions at once: from droughts in the Americas to floods in Asia, and to heatwaves and forest fires across Europe and beyond. The scale of these anomalies can be difficult to grasp. To help, The Economists data team have brought together and updated four of our recent charts showing how the run of extremes in 2023 compares with conditions in previous years (see below). Start with air-temperature records. Estimates of Earths average temperature have already hit new highs four times this year, according to estimates from the European Centre for Medium-range Weather Forecasts. The first, set on July 3rd, was 0.086C higher than the previous peak, reached last yearthe biggest margin ever recorded. On the next day that difference doubled. The most recent, on July 6th, was 17.079C, around 0.8C warmer than the hottest temperature recorded in 1980. A string of records in an El Nino year is not in itself surprising (see 2016). What is remarkable about this year is that, over the three weeks that followed the initial record, the temperature never fell below the previous record, from 2016. Not surprisingly, on July 27th Copernicus and the World Meteorological Organisation confirmed that this July is set to be the hottest of any month on record. Our second graphic shows where the world has been hotter than it normally is at this time of year, illustrating the current heatwaves. It compares the temperatures between July 1st and 20th this year with the average from the same period in 1991-2020. Parts of southern Europe have been between 2C and 5C warmer in July than the historical average. Two heatwaves brought sweltering temperatures to France, Germany, Italy, Spain and Poland. An atmospheric heat dome, a slow-moving area of high pressure, has enveloped the southern part of the continent, reducing cloud cover and allowing more solar radiation to heat the ground. World Weather Attribution, a network of climate modellers, has said that these heatwaves would have been virtually impossible before humans began pumping large quantities of greenhouse gases into the atmosphere. Now they can be expected roughly once in every ten years. Even larger heat anomalies have been felt across Newfoundland, in north-eastern Canada, where temperatures in some parts were more than 8C higher than normal. The third chart focuses on sea-surface temperatures. Oceans have soaked up about 90% of the excess heat caused by greenhouse-gas emissions in recent decades and the temperature of surface waters has gradually increased. This years rise has been particularly alarming. Ocean temperatures normally peak in March (the end of summer in the southern hemisphere, where most of the surface is ocean) and gradually cool until June or July. This year, however, the drop never came. Sea-surface temperatures in July have been around 0.25C above their previous daily records for the month. And temperatures are still rising: between July 16th and 23rd sea-surface temperatures were higher than at any other point this year. They are currently only 0.01C below the record set in March 2016. Finally, observe the dramatic decline of sea ice in the far south. Satellite data show that the ocean around Antarctica has less sea ice than has ever been measured before in July. On July 24th the sea ice covered just 14m square km. That is around 2m square km less than in 2019, the previous record low for that date; it is roughly 3m square km less than the average for 1991-2020. To put that in context: 14m square kilometres is one and a half times the area of the United States; 2m square kilometres is about the size of Mexico. Are these charts evidence that climate change is speeding up? Some scientists reckon that the rate at which the world is warming seems to have gone through a step change in the 2010s. So far, though, there is no consensus on that, and current anomalies, though suggestive, are not in themselves enough to bring one about. What is known is that more greenhouse gas in the atmosphere results in more of the warmth from the sun being trapped near the surface and absorbed by the oceans. Carbon dioxide, the most important long-lived greenhouse gas, has reached its highest level in over 3m years, according to one reading. Levels of methane and nitrous oxide, two other long-lived greenhouse gases, are also at the highest since humans appeared. Some years are hotter than others; this may just be a particularly hot year in a world whose climate has already warmed. Next year, or the year after, may be a little cooler. But decade by decade the picture is clear. Every decade since the 1980s has been considerably hotter than the one which came before. The 2020s will be hotter than the 2010s. The 2030s will be hotter still.