Oxford (UK), January 12 (The Conversation) Earth's climate will experience its hottest year on record in 2024. Severe floods in April killed hundreds of people in Pakistan and Afghanistan. A year-long drought has dropped the water level of the Amazon River to its lowest level ever. And in Athens, Greece, the ancient Acropolis closed at noon to protect tourists from the dangerous heat. A new report from the EU's Copernicus Climate Change Service confirms that 2024 will be the first year on record in which global average temperatures will exceed pre-industrial levels by 1.5 degrees Celsius.
All continents except Australia and Antarctica experienced their hottest year on record, with 11 months of the year exceeding 1.5 °C. Global temperatures have been at record lows for several years – and are still rising. The previous hottest year on record was 2023. The ten hottest years on record have all occurred in the last decade. But this is the first time any calendar year has crossed the 1.5°C threshold.
Copernican scientists used reanalysis to calculate temperature increases and estimate changes in extreme events. The reanalysis is produced in real time, combining observations from as many sources as possible, including satellites, weather stations and ships, with a state-of-the-art weather forecast model, to create a complete picture of the weather around the world over the past year.
The resulting dataset is one of the major tools used by scientists globally to study weather and climate. Limiting sustained global warming to 1.5 degrees Celsius is a key goal of the Paris Agreement, a 2015 international treaty that aims to mitigate climate change. The 195 signatory countries pledged to “step up efforts” to keep long-term average temperature rise well below 1.5 degrees Celsius.
Reaching 1.5°C by 2024 is a milestone, but exceeding 1.5°C warming in a year is not the equivalent of crossing the Paris limit. Year-to-year variations in climate mean that even if temperatures rise by more than 1.5 °C in one year, the long-term average may remain below that level. This long-term average temperature is mentioned in the Paris Agreement. The current long-term average is about 1.3 °C.
Natural factors, including a strong El Niño, contributed to the increase in temperatures in 2024. El Niño is a climate phenomenon that affects weather patterns on a global scale, causing increased ocean temperatures in the tropical Pacific.
This could raise global average temperatures and increase the likelihood of extreme events in some parts of the world. While these natural fluctuations exacerbated human-caused climate change in 2024, in other years they act to cool the Earth, reducing the temperature increase seen in a particular year.
While goals focus the minds of policy makers, it is important not to focus too much on what the goals are, from a scientific perspective. Research has shown that catastrophic effects, such as the rapid and potentially irreversible melting of the Greenland ice sheet, become more probable with every small amount of warming.
These effects can occur even when boundaries are crossed only temporarily. In short, every tenth degree of warming matters. What ultimately affects humans and ecosystems is how global climate change manifests in regional climate and weather. The relationship between global climate and weather is non-linear: 1.5 °C global warming could lead to individual heatwaves that are much hotter than the average increase in global temperatures.
Europe recorded its hottest year on record in 2024, manifesting as severe heatwaves, especially in southern and eastern Europe. Wildfires destroyed large areas of pine forests and homes in parts of Greece and the Balkans. This new report shows that 44 percent of the world experienced severe or high heat stress on July 10, 2024, which is 5 percent more than the average annual maximum.
Especially in low-income countries, this can lead to poor health outcomes and more deaths. The report also notes that the amount of atmospheric moisture (precipitation) in 2024 was 5 percent more than the average of recent years. Warmer air can hold more moisture and water is a powerful greenhouse gas, trapping even more heat in the atmosphere.
More worryingly, this higher moisture content means that extreme rainfall events may become more intense. In 2024, devastating floods occurred in many areas, such as the floods that occurred in Valencia, Spain last October. It's not so simple that more moisture content leads to more rainfall: the winds and pressure systems that move the weather around also play a role and can be affected by climate change.
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