How much has the Earth warmed in last 240 years?
What's the story
A new temperature dataset, GloSAT, has been released by a team of UK-based scientists. The dataset goes back to 1781, challenging the conventional start year of 1850 for measuring global warming. The new record indicates that greenhouse gases rose by 2.5% between 1750 and 1850, possibly causing more warming than previously calculated.
Temperature shift
New dataset reveals cooler Earth before 1850
The GloSAT dataset shows a much cooler Earth from the late 1700s to 1849 compared to the "preindustrial" baseline period of 1850-1900. Two volcanic eruptions in the early 1800s had a cooling effect on global temperatures. The United Nations Intergovernmental Panel on Climate Change (IPCC) also suggested possible human-caused warming between 1750 and 1850, estimating it at up to 0.2 degrees Celsius.
Human influence
New studies estimate human impact on warming
A study using the GloSAT dataset estimated a human-caused warming of 0.09 degrees Celsius between 1750 and 1850. Another study arrived at a similar conclusion, estimating an additional 0.1 to 0.2 degrees Celsius of warming due to early carbon dioxide increases. These findings highlight the complexity of attributing temperature changes to human activities and natural factors like volcanic eruptions.
Historical data
Old temperature records contribute to new dataset
The GloSAT dataset relies on old temperature records, such as those from Hohenpeissenberg in the Bavarian Alps since 1781. These records show significant regional warming. However, measuring ocean temperatures remains a challenge due to sparse historical data. Ships of the British East India Company and whaling vessels also recorded marine air temperatures, contributing to the dataset's accuracy.
Cautious conclusions
Scientists caution against overinterpreting new findings
While the new dataset indicates more warming than previously thought, scientists urge caution in interpreting these findings. Zeke Hausfather from Berkeley Earth cautioned against jumping to conclusions that this undermines climate goals like those in the Paris Agreement. Peter Thorne, a climate scientist at Maynooth University, emphasized that while earlier warming is significant, it doesn't necessarily mean impacts will occur sooner than expected.