Earth's hottest 12 month period with most of the temperature increase due to burning fossil fuels

Analysis by climate scientists at Climate Central has highlighted we have just gone through the hottest 12 month period in recorded history (November 2022-October 2023), with an average global  temperature of 1.3C above pre-industrial temperatures.

The Copernicus Climate Change Service (C3S) also reported that 2023 is on track to become the warmest year after record October. They report that October 2023 was 1.7°C above the average for 1850-1900, designated as the pre-industrial reference period. October marked the fifth consecutive month of record temperatures globally.

"October 2023 has seen exceptional temperature anomalies, following on from four months of global temperature records being obliterated. We can say with near certainty that 2023 will be the warmest year on record, and is currently 1.43°C above the preindustrial average. The sense of urgency for ambitious climate action going into COP28 has never been higher," said Samantha Burgess, C3S’ Deputy Director.

Copernicus Climate Change Service  also reported the Sea surface temperature for the extrapolar oceans (over 60°S–60°N) was the highest on record for October at 20.79°C 

Analysis using Climate Central’s Climate Shift Index shows:

• how human-caused climate change influenced heat over the last 12 months in 175 countries and 920 cities.
• Over that time, 90% of people worldwide (and 49% in the U.S.) experienced at least 10 days of temperatures very strongly influenced by climate change.
• One-in-four people on Earth faced extreme, persistent, and dangerous heat waves driven by carbon pollution.
• Out of 700 largest cities, Houston, Texas experienced the longest streak of extreme heat made more likely by carbon pollution: 22 days.
• The rising frequency and intensity of heat waves across the globe is consistent with the consequences of carbon pollution — mainly from burning coal, oil, and natural gas. 

Climate change attribution science quantifies whether and to what extent human-caused climate change altered the likelihood of specific extreme weather events.  According to Climate Central’s daily attribution system, the Climate Shift Index (CSI), the latest peer-reviewed methodology to map the influence of human-caused climate change on daily local temperatures and multi-day extreme heat events across the globe.

The analysis using the Climate Shift Index (CSI) quantified the influence of human-caused climate change on extreme heat in 175 countries and 920 cities during Earth’s record-hottest 12 month period (November 1, 2022 to October 31, 2023). 

It found:

• The past 12 months (November 1, 2022 to October 31, 2023) were Earth’s hottest on record. Over this period, the global average temperature was 1.3°C (2.3°F) above pre-industrial temperatures. 
• Over the last 12 months, 7.3 billion people (90% percent of the global population) experienced at least 10 days of temperatures strongly affected by climate change. These days had a CSI level of 3 or higher, indicating that human-caused climate change made those temperatures at least three times more likely. 
• During the same period, 5.8 billion people (73% of the global population) experienced more than a month’s worth of these temperatures. 
• Jamaica had the highest average CSI of any country analyzed (4.5 out of a maximum of 5). On the average day over the last 12 months, Jamaicans experienced average temperatures made at least four times more likely by human-caused climate change. 
• The influence of carbon pollution on heat was strongest in the developing world. Extreme heat driven by climate change is also accelerating among the world’s richest countries. 

Climate Central also analyzed how climate change influenced exposure to extreme heat (above the local 99th percentile) that persisted for at least five days. Over the last 12 months, 1.9 billion people (one in four people) experienced an extreme heat streak that lasted at least five days and was strongly influenced by carbon pollution. These multi-day heat streaks had a CSI of 2 or higher, indicating that human-caused climate change made those temperatures at least two times more likely.

References:

Climate Central, 9 November 2023, Earth’s hottest 12-month streak https://www.climatecentral.org/climate-matters/earths-hottest-12-month-streak-2023 

Nature news, 10 November 2023, Earth just had its hottest year on record — climate change is to blame,  https://www.nature.com/articles/d41586-023-03523-3 

Copernicus Climate Change Service (C3S), 10 November 2023, 2023 on track to become the warmest year after record October https://climate.copernicus.eu/2023-track-become-warmest-year-after-record-october