If you’ve checked out parts 1 and 2 of this three-part series examining the new State of the Climate 2023 report, you already know that greenhouse gases have been continuing their relentless growth in the atmosphere, and that 2023 shattered previous global heating records.
Here in Part 3 of the series, I look at some of the other impacts, starting with one that took me surprise: In addition to being the warmest year, 2023 was also the least cloudy ever observed globally in records dating back four decades. Some areas saw particularly steep declines in cloudiness, including the Indian Ocean, the Arctic, and Northern Hemisphere.
The global average for cloud cover in 2023 was the lowest ever recorded. In this map, areas colored in brownish tones saw less cloud cover than normal. (Credit: State of the Climate in 2023 report, Bulletin of the American Meteorological Association)
Over the long term, cloudiness has been declining at a rate of .62 percent per decade since the start of the record in 1980, according to the report.
By affecting how much of the Sun’s energy reaches the surface, and how much heat escapes into space, clouds have a profound impact on the climate. In 2023, the report concludes that clouds reflected away to space the smallest amount of energy from the Sun ever observed. That meant more solar energy reached the surface to cause warming. But at the same time, clouds blocked the least amount of heat energy from escaping to space from the surface.
Teasing out the net effect from changes in cloudiness is complicated, because different kinds of clouds have different impacts. With that caveat in mind, the report concludes that the overall impact “was the weakest cooling effect of clouds on record.” And this, in turn, reinforced 2023’s shocking warmth.
Paltry Precipitation
The clearer skies may also have contributed to less precipitation than normal. In fact, the amount of precipitation that fell during the year was one of the lowest in records going back to 1979. At the same time, the intensity of rain that did fall increased, which can contribute to damaging deluges.
As the report points out, this is just what scientists have long expected with a warming climate.
Heat and paltry precipitation is a recipe for drought. And that’s precisely what the climate system cooked up.
This map reveals patterns of drought globally in 2023, with brown colors indicating drier than normal conditions. (Credit: State of the Climate in 2023 report)
The world has been experiencing an increasing trend in the severity and extent of drought since 1950. In July of 2023, that trend culminated in a new record being set for the portion of Earth’s land surface that was experiencing extreme drought: 7.9 percent. By a wide margin, this broke the previous record set a year earlier. And it was the first time that more than 7 percent of Earth’s land surface experienced extreme drought.
A much larger portion of Earth’s land surface fell into at least moderate drought during the year: just shy of 30 percent, setting a new record as well. Worst hit were parts of South and North America, the Mediterranean, and the midlatitudes of Asia.
Scorched Earth
An aerial view of smoke from wildfires in Alberta, Canada, photographed on May 5, 2023. (Credit: Alberta Forestry and Parks)
The report notes that 2023 was North America’s warmest year in records extending back 114 years to 1910. At the same time, all three North American countries — the United States, Mexico and Canada — experienced widespread drought events, with Mexico reporting its driest year on record.
With that in mind, it probably should come as no surprise that several extreme wildfire events occurred during the year. The wildfire season in Canada was particularly severe, with about 15 million hectares scorched, according to the report — an area more than twice the size of Ireland. That obliterated the previous record for most area burned in Canada in a single year — more than doubling what was experienced in 1989.
Early snowmelt combined in 2023 with drought and exceptional warmth to help produce Canada’s worst wildfire season on record by far. The chart shows the annual area burned in the country from 1986 to 2023, in millions of hectares. The inset map shows the perimeters of wildfires during the year. (Credit: State of the Climate in 2023 report)
“Sustained fire weather conditions primed the landscape, allowing for fire growth following ignition, which was caused by lightning for most of the large fires,” according to the report. High winds often fanned the flames. As a result, “already-large fires experienced rapid spread.”
Smoke from the blazes was snared by weather systems and the jet stream, which blew it across a vast territory. Smoke smothered cities as far away as New York — and it even was swept all the way across the Atlantic Ocean to Western Europe.
Carbon dioxide released by these and other fires worldwide, made a significant contribution to total emissions in 2023, according to the report.
Shrinking Ice and Rising Seas
The record-shattering heat of 2023 continued a decades-long trend that has propelled a relentless rise of sea level threatening tens of millions of coastal dwellers worldwide.
The oceans have been absorbing more than 90 percent of the heat trapped in the climate system as a result of our greenhouse gas emissions. And lucky for us! Otherwise, the heat waves and other extremes we’ve been experiencing would be far worse.
But ocean water expands as it heats up, making this one of the biggest contributors to sea level rise. And in 2023, the word’s oceans heated up significantly: The amount of heat stored in the in the top 2,000 meters (6,500 feet) of the oceans rose to a record high level.
Hikers descend Longyearbreen, a glacier near Longyearbyen in Norway’s Arctic archipelago of Svalbard. Ice mass losses from melting and runoff have been outpacing accumulations from snow, causing Svalbard to lose more ice than it gains — just one sad part of a global trend. (Credit: © Tom Yulsman)
Alpine glaciers contributed to sea level rise in 2023 by shedding meltwater into rivers and ultimately the sea. Analysis of one glacial dataset revealed that 108 out of 109 glaciers on six continents lost mass during the year.
All in all, 2023 was the 36th consecutive year that alpine glaciers lost mass through melting and calving of ice.
Some glaciers gave up the ghost completely in 2023. These included Switzerland’s St. Anna Glacier and the Ice Worm Glacier in the United States, which disappeared due to rapid losses that began in 2021. These were small glaciers, but their disappearances “are reflective of the global pattern of glacial mass loss,” the report states.
Losses from the giant ice sheet in Greenland have been contributing significantly to sea level rise. Satellite measurements suggest that from 2002 up to 2023, Greenland had been shedding 270 billion tons of ice to the sea each year. During the same period, Antarctica lost about 100 billion tons each year.
Focusing on Antarctica in particular, the authors of the State of the Climate report estimate that its ice sheets significantly topped that figure in 2023, shedding a whopping 170 billion tons of ice.
Yet Another Record Set in 2023
Ice losses and ocean thermal expansion added up to a record-setting year for sea level rise. According to the report, global mean sea level reached a new record high in 2023 for the 12th consecutive year. The rise over 2022 was the third highest year-over-year increase on record.
Overall, just as growth rate of CO2 in the atmosphere has been increasing, the rate of sea level rise has been accelerating.
As I pointed out in Part 1 of this series, there is still cause for hope: Emissions of CO2 by the most advanced economies of the world have peaked and are dropping — even as economic growth continues. They’re accomplishing this through efforts to use energy more efficiently, along with a massive ramp-up in renewables. And this points the way forward toward a day when we may finally tame the climate crisis.
But we have a long way to go. Last year’s truly shocking climate extremes should serve as warning to us that if we don’t get our act together soon as stewards of the climate system, we are going to be in for a world of hurt.
For Part 1 of this series, please go here. And for Part 2, click here.
Source : Discovermagazine
