What does this mean for global warming?Using this new baseline, a very different picture of global warming emerges. It shows human-caused ocean warming began at least several decades earlier than previously assumed by the IPCC.Long-term climate change is commonly measured against the average warming over the 30 years from 1961 to 1990, as well as warming in more recent decades.Our findings suggest that in the interval between the end of our newly defined pre-industrial period and the 30-year average mentioned above, the temperatures of the ocean and land surface increased by 0.9°C. This is far more than the 0.4°C warming the IPCC has estimated, using the conventional timeframe for the pre-industrial period.Add to that the average 0.8°C global warming from 1990 to recent years, and the Earth may have warmed on average by at least 1.7°C since pre-industrial times. This suggests we have passed the 1.5°C goal of the Paris Agreement.It also suggests the overriding goal of the agreement, to keep average global warming below 2°C, is now very likely to be exceeded by the end of the 2020s – nearly two decades sooner than expected.Our study has also produced another alarming finding. Since the late 20th century, land-air temperatures have been increasing at almost twice the rate of surface oceans and are now more than 2°C above pre-industrial levels. This is consistent with a well-documented decline in Arctic permafrost and the increased frequency around the world of heatwaves, bushfires and drought.We must act nowOur revised estimates suggest climate change is at a more advanced stage than we thought. This is cause for great concern.It appears that humanity has missed its chance to limit global warming to 1.5°C and has a very challenging task ahead to keep warming below 2°C. This underscores the urgent need to halve global emissions by 2030.
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