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The analysis calculated climate change attribution assessments for 4,700 cities and 200 countries, finding that residents in various major cities with population above 6 million were exposed to average monthly temperatures made at least 3 times more likely by climate change.
“Human-caused climate change influenced July temperatures for the vast majority of humanity,” Dr Andrew Pershing, vice president for science at Climate Central said. “Across the entire planet, the average person was exposed to 11 days in which carbon pollution made the local temperature at least three times more likely. Virtually no place on Earth escaped the influence of climate change last month.”
The influence of climate change for this analysis was assessed using the Climate Shift Index, which applies a peer-reviewed model- and observation-driven methodology to determine the likelihood of local, daily temperatures with and without current levels of carbon pollution. The change in likelihood is scored on a five-point scale, with 1 (at least 1.5 times more likely) through 5 (at least 5 times more likely) representing temperatures made more common by climate change.
Climate Central’s Climate Shift Index (CSI) tool quantifies the local influence of climate change on daily temperatures around the world.
The CSI quantifies how much human-caused climate change has shifted the odds of daily temperatures that people experience locally. The CSI tool is grounded in peer-reviewed attribution science and was launched by Climate Central in 2022.
The Climate Shift Index is based on the ratio of the local frequency of a particular daily temperature in the current climate to the estimated frequency of that temperature in a world without human-caused climate change.
The Climate Shift Index (CSI) has 11 levels that indicate how climate change has altered the frequency of daily high, low, and average temperatures at a given location.
CSI levels from 1 to 5 indicate that human-caused climate change has made the observed or forecasted temperatures more likely or, equivalently, more common.
CSI levels from -1 to -5 indicate temperatures that are becoming less likely or less common due to human-caused climate change. On an example the CSI level of 3 indicates local conditions that were made at least three times more likely due to climate change.