In the first of this three-part series highlighting the new Climate Change 2023 report, we discussed the relentless increase in greenhouse gases in the atmosphere. Far from showing any signs of leveling off (and they must soon if we are to avoid even more destructive climate change than we have seen so far), the rate of increase is accelerating.
In fact, 2023 was the fourth highest year on record for atmospheric CO2 concentrations.
As I pointed out in Part 1, no aspect of Earth’s climate life support system has escaped the effects of the ever-thickening layer of greenhouse gases that we have released onto the planet in the last year. Climate Situation Report 2023Of course, this includes rising temperatures globally, and that’s what I’m focusing on here. (See the end of this article for links to the other articles in this series.)
Frankly, global warming has reached completely abnormal levels in 2023. In records going back to 1850, the global annual average surface temperature was by far the highest ever observed.
This map shows how average land surface temperatures in 2023 have changed from the long-term average. (Credit: NOAA/NCEI)
Analysis of seven separate datasets reveals that global surface temperatures in 2023 will be 0.55 to 0.60°C warmer than the 1991-2020 average. This will be the highest on record and significantly surpass the previous record of 2016.
The current state of the climate analysis compared global average temperatures in 2023 to pre-industrial temperatures, before humans began emitting large amounts of greenhouse gases into the atmosphere. Last year, global surface temperatures were 1.35°C to 1.54°C warmer than the pre-industrial average, according to the report.
“Dozens of countries reported record or near-record heat this year, including China and the whole of continental Europe (highest on record), India and Russia (second highest), and Canada (third highest),” the report said. Additionally, “intense and widespread heatwaves were reported around the world.”
The unusual global warming of 2023 is not a one-off phenomenon: All seven data sets agree that 2015-2023 was the warmest nine-year period since world records began. And the heat is continuing: Every month up until July this year saw record global temperatures. According to NOAA.
As of 2024, last month was the warmest July globally in NOAA’s 175-year record keeping. This marked the 14th consecutive month of record-breaking global temperatures, breaking the longest consecutive hot spell in modern records. The previous record for the warmest temperature on record was from May 2015 to May 2016.
Ocean Warming
Between 1971 and 2020, the oceans absorbed about 89 percent of the heat that entered the Earth’s climate system from greenhouse gas emissions. This heat accumulation is greatest and most evident at the surface, the 2023 State of the Climate report notes.
In 2023, global sea surface temperatures broke all-time records, and record-breaking sea surface temperatures are set to continue into 2024, only showing signs of cooling in recent weeks.
As an aside, this cooling trend is likely to continue as the La Niña weather phenomenon becomes more established. This weather phenomenon is characterized by lower-than-average sea surface temperatures in the tropical Pacific Ocean and tends to lower the global average temperature.
However, climate models suggest that the La Niña event will be weaker and have a later onset than previously thought (for an update on this, see this post on the always excellent ESNO blog). August 2024 outlook: La Niña phenomenon emerges during extremely hot summer.
Fast forward to 2023, and a new report reveals that a shocking 94 percent of the world’s ocean surface has experienced at least one marine heatwave. These temporary periods of abnormally high ocean temperatures can intensify tropical cyclones, as well as bleach coral and damage marine ecosystems, including the fisheries that millions of people around the world depend on for food.
Typically, marine heatwaves occur about 10 percent of the time in any given location. But the report said that in 2023, marine heatwaves far exceeded normal levels and “record-breaking extreme events (in terms of extent and intensity) were observed around the world.”
2023 will see 116 marine heatwave days throughout the year, far surpassing the previous record of 86 days set in 1982.
These maps show the intensity of heat stress on corals during global coral bleaching events in 1998, 2010, 2014-2017, and 2023-2024. Heat stress is ranked on a scale of 1 to 5. (Credit: NOAA)
Marine ecosystems are suffering greatly, as evidenced by the severity and extent of coral bleaching events. This occurs when corals become so stressed by rising ocean temperatures that they expel their symbiotic algae and turn a ghostly white. Bleached corals can survive, but if the stress is too high and sustained, they will eventually die.
Coral bleaching around the world has been particularly severe in 2023 and continues into this year. Recent NOAA ReportsMass coral bleaching has been confirmed in all ocean areas containing warm-water corals and in at least 62 countries and territories around the world from early 2023 until at least mid-May 2024.
Next up…
The unusually high global warming in 2023 was accompanied by a range of impacts, including accelerated ice loss, sea level rise, changes in cloud cover, reduced average precipitation and increased short-term heavy rainfall, and expanded droughts. In the final part of this series, we will focus on these impacts.
For part 1 of the series, hereFor part 3 here.
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