Climate change: atypical heat of July was felt by almost entire planet

As per a recent investigation, over 80% of the world's population experienced the intense heat of July firsthand, making it the hottest month on record so far. To put it differently, four out of five people lived in cities where the average temperature in July was influenced, at least for a day, by the effects of climate change.

When they refer to July as the hottest month, they are talking about the average global temperature across the entire Earth. However, people cannot directly sense this record-breaking heat. Instead, we experience the impact of climate change through observable changes in daily temperatures and weather patterns in the local areas where we reside. This measurement and analysis were conducted by Climate Central, a nonprofit organization established by scientists and journalists.

The researchers analyzed data from 4,711 cities in 200 countries around the world. And 4,019 of these cities were found to be impacted by climate change. The impact affects 6,500 million people.

The new study says that burning coal, oil and natural gas made it three times more likely to be hotter in at least one day in these regions.

Everything was worse in the tropics, near the equator. In this region, at least 2 billion people—a quarter of the planet's population—felt a very strong influence of climate change every day of July. For example, the report says, the levels of heat experienced in the southern United States, Mexico, Central America, and the Caribbean would have been extremely unlikely without the human-caused climate emergency.

Observed temperature variations and patterns.

The hottest day worldwide was on July 7. But the effect of climate change was felt in more places on July 10, the Climate Central report notes. The organization estimates that around 3.5 billion people experienced unusual heat during that day.

Climate Central asserts that temperature fluctuations are linked to climate change, a result of human activities. The organization introduced the Climate Change Index a year ago, a tool that assesses the real-time impact of climate change on global temperatures.

Utilizing observations and computer simulations from US and European scientists, the index determines the effect by comparing current temperatures with a simulated world unaffected by climate change, which is 1.2 degrees C colder – the estimated warming since the Industrial Revolution. This five-point scale indicates the increased likelihood or frequency of daily temperature changes due to climate change.

Record July heat linked to climate change

In July 2023, global average temperatures reached unprecedented levels, accompanied by widespread local heat extremes—dangerous weather events with severe consequences.

Utilizing the Climate Shift Index, Climate Central's daily temperature attribution tool, analysis shows that human-induced climate change played a significant role in amplifying the extreme heat experienced during the month.

Approximately 2 billion people worldwide, constituting a quarter of the global population, felt a substantial impact of climate change on each day in July. Human-caused climate change particularly affected temperatures for people living near the equator and on small islands.

In regions such as the southern U.S., Mexico, Central America, and the Caribbean, the intensity of July's heat would have been highly improbable without human-caused climate change.

In the U.S., at least one day in July saw temperatures made at least three times more likely due to human-caused climate change, impacting a staggering 244 million people, which represents 73% of the population.

Specific U.S. cities with the most pronounced climate fingerprints on July's heat included Cape Coral, Fla.; Sarasota, Fla.; Bonita Springs, Fla.; Santa Fe, N.M.; Miami, Fla.; Mesa, Ariz.; and Albuquerque, N.M.

U.S. cities with strongest climate change fingerprints in July 2023

There were 25 U.S. cities with an average CSI level of 3 or higher in July 2023, 19 of which had at least 21 July days with CSI levels of 3 or higher:

Climate change fingerprints on extreme July heat events in U.S. cities. 

The following U.S. cities all had CSI levels of 5 (the maximum on the scale) during their most intense 14-day heat events in July 2023. CSI level 5 events would be very difficult to encounter in a world without human-caused climate change—not impossible, but extremely unlikely.

The new normal?

The Climate Central study lacks peer review, crucial for scientific credibility. However, external climatologists consulted by AP found it credible, citing the organization's use of recognized "climate fingerprinting" methods endorsed by the US National Academy of Sciences.

Andrew Pershing, Climate Central's VP of science, highlighted that climate change is increasingly becoming the new normal, with its effects felt almost everywhere.

Even in the southern hemisphere's winter, cities in Chile and Argentina are experiencing unusual heat spikes, such as Buenos Aires hitting 30°C, the highest August temperature on record, compared to the usual 10-16°C for this time of year.

Gabriel Vecchi, a Princeton University climatologist, stated, "We should now expect individual heat waves to be connected to global warming," and the extreme heat experienced in July gave most people on Earth a glimpse of the impact of global warming.

What is the Climate Shift Index (CSI)?

In 2023, global average temperatures reached an unprecedented level. However, people do not directly encounter global average temperatures. Instead, they primarily experience climate change through changes in the daily temperatures and weather patterns in their respective locations.

The Climate Shift Index (CSI) tool of Climate Central quantifies the local influence of climate change on daily temperatures around the world.

The CSI tool quantifies how much human-caused climate change has shifted the odds of daily temperatures that people experience locally. Climate Central launched the CSI tool in 2022, grounding it in peer-reviewed attribution science. Access to the CSI tool is free.

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. 

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