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Climate crisis 9111911 More than a quarter of the American population is experiencing above-average temperatures. 499 counties have already reached 1.5C (2.7F) heat, according to a Guardian analysis of climate data.| Climate crisis

Climate crisis 9111911 More than a quarter of the American population is experiencing above-average temperatures. 499 counties have already reached 1.5C (2.7F) heat, according to a Guardian analysis of climate data.| Climate crisis

More than a third of the American population is currently experiencing rapid, above-average rates of temperature increase, with 499 counties already breaching 1.5C (2.7F) of heating, a Guardian review of climate data shows.

The US as a whole has heated up over the past century due to the release of planet-warming gases from burning fossil fuels, and swathes of the US west, northeast and upper midwest representing more than 124.6 million people have recorded soaring increases since federal government temperature records began in 1895.

Although the US is currently experiencing a climate crisis, it is not happening in a uniform way. Many of America’s largest cities have seen extreme warming hotspots, as well as places as diverse as California’s sunny coast and the previously cold northern reaches Minnesota. Other places, especially in the south, have not seen their temperatures change much.

Map showing the temperature changes in US counties between 1895-1821.

Brian Brettschneider (an Alaska-based climate scientist) said that the warming isn’t evenly distributed. He collated the temperature data for each county from the National Oceanic and Atmospheric Administration. While many places have seen dramatic changes in their climate, there are still some places that are below the average. The impacts vary depending on where you are.

According to Noaa data Ventura county in California has seen its temperature rise more than any other county within the contiguous US. It experienced a 2.6C (4.75F), increase of total warming during the period 1895 to 2021. The average temperature in many American cities, including New York City, Los Angeles, Miami and Philadelphia, has risen far above the national average of 1C (1.8F) since pre-industrial times.

The table below shows the top US counties that experienced the greatest temperature increases between pre-industrial and modern times.

Mark Jackson, a meteorologist with the National Weather Service, Oxnard, Ventura county, said that the county’s temperature rise is remarkable. It is scary when you consider the rate at which we are looking. Jackson stated that the county has experienced a significant increase in heatwaves. This included a spell of over 37C (100F), last summer, which really stressed the community.

Ventura county is located on the Californian coast northwest from Los Angeles. It is known for its Mediterranean climate that is slightly cooled by the ocean. Jackson said that recent heatwaves saw warm air flow downhill from nearby Los Padres National Forest, to the coast, and the ocean itself is being roiled due to rising temperatures. It has been amazing to see it get so hot right up to where the coast is, he said.

California is in the grip of its most severe drought in 1,200 years and scientists say this is fueling the heat seen in many places in the state Los Angeles has warmed by 2.3C (4.2F) since 1895, while Santa Barbara has jumped by 2.4C (4.38F) by reducing moisture in soils, which then bake more quickly.

The state is also at greater risk from wildfires due to higher temperatures. We lost everything, said Tyler Suchman, founder of online marketing firm Tribal Core who in 2017 fled with his wife to escape a huge wildfire that razed their home in Ojai, in Ventura county. It was terrible. It was terrifying. The wind was blowing so fast that the hills along the highway were on fire.

Just 11 months later, a separate wildfire destroyed the couples next home, in Malibu, as their neighbor scooped up water from his hot tub in a desperate attempt to tackle the flames. Suchman stated that no one wants us moving next to them. It is easy to see the changes in the area over the 18 years since our move to Ojai. It is a beautiful place, but we cannot live there at the moment because of the dangers.

All across the US, there are hotspots of above average warming. Grand county, Utah, is a place with sprawling deserts and cliffs. Every county in New Jersey (Massachusetts) has warmed by over 1.5C (2.7F) in the past 1895.

The area bar chart shows how much of each state’s population lives in counties where there has been a warming trend of +1.5C.

The most recent extreme heat has been experienced in the northern latitudes. However, Alaskan counties have been the top six most warming places since 1970 (comparable temperatures data for Alaska do not go back further than 1920s). The Arctic has warmed up to the North slope of Alaska, which is located in the rapidly warming Arctic. It has risen by an astounding 3.7C (6.6F).

There really is a climate shift underway in Alaska, everyone can see things are different than they used to be and everyone is concerned about what the future here will look like, said Brettschneider, who said even his teenage children have noticed the retreat of sea ice, an elongating fire season and a dearth of cold days.

The warmth is also melting the frozen soils known as permafrost. This causes buildings to collapse and roads to buckle. Katharine Hayhoe (climate scientist at Texas Tech University and chief scientist for the Nature Conservancy) said that it is like driving on a rollercoaster.

Other places that used to be subjected to severe cold also have seen significant temperature increases. Roseau and Kittson, both in northern Minnesota, are among the top five most warming counties in the lower 48. Their warming is due to winters that have warmed up by approximately 3.8C (7F) since modern records began.

Winters are warming faster than summers, as more heat is lost during the colder months. However, greenhouse gases are trapping it. Although some may say they like warmer winters, people are seeing negative impacts such as changes in the growing seasons and the loss of cultural practices, such as cross-country ski races, according to Heidi Roop, a University of Minnesota climate scientist. Even small temperature fluctuations can have huge consequences.

In 2015, the Paris climate agreement established a global goal for governments to limit the rise in temperature by 1.5C (2.7F) over the pre-industrial era. Scientists warn that the world faces increasingly severe heatwaves and storms, flooding, and social unrest beyond this point.

Hayhoe stated that although some areas in the US have already exceeded 1.5C, the most important metric is still global average. A 2C increase is acceptable in some places, but 2.5C is when things get crazy. Some areas can handle 5ft of sea-level rise due to their elevation, while others can’t because they’re too low. Local vulnerability is highly individual. It doesn’t matter to communities if the world meets their targets, it’s a collective goal for the entire world.

That global threshold is in severe peril, with some forecasts warning that 1.5C (2.7F) could be breached within a decade without drastic cuts to carbon emissions. Roop says that communities will need to prepare for the consequences.

She stated that the rate of warming is exceeding what we believed was possible. We are already paying the consequences and must prepare for the changes in the future as well as to prevent further heating.