Climate Change Fuels Record Hot Summer’s Latest Heat Waves

La Taina Del Caribe, Creative Commons

Climate change amplified heat waves break records in the US and worldwide

The Japanese Meteorological Agency has announced that this past July was the warmest on record, a finding reinforced by preliminary NASA data. This means July was likely the hottest of any month on record, and puts 2015 safely on track to beat 2014 as the hottest year on record.

More recently, climbing temperatures and out of control wildfires are spreading across the West, marking the start of a scorching heat wave. Southern California saw record high temperatures and burgeoning wildfires this past weekend. Santa Cruz broke its daily high temperature record for August 15, and San Francisco, its daily high for the following day. The heat wave also saw Phoenix tie its monthly heat record for August at 117°F, as well as low temperatures in the city that did not drop below 93°F for three consecutive days. As we enter the new week, record-challenging heat is building in the Northwest, which will worsen wildfires fueled by heat and dryness.

Meanwhile, after a weekend of temperatures exceeding 90°F, many cities in the Northeast will enter a heat wave on Monday, with high temperatures and humidity levels in DC, New York, Boston and surrounding areas.

One of the clearest findings of climate science is that global warming amplifies the intensity, duration and frequency of extreme heat events, as our extreme heat backgrounder explains.

  • The link between climate change and extreme heat is firmly established. Even a small-seeming change in average global temperature—0.72°C (1.3°F) since 1951—can lead to dramatic regional changes in extreme events. Due to global warming, rare extreme heat events impact a percentage of the globe 10 times greater than they did from 1951-1980.
  • Climate change has already increased the intensity, duration and frequency of extreme heat events and will continue to amplify these events in the future. Global warming has doubled Europe’s risk of heat waves. A January 2015 study found that during the period 1973-2012, many urban areas across the globe experienced significant increases in the number of heat waves, with the largest number of heat waves occurring in the most recent decade studied, 2003-2012. Another study found that seventy-five percent of moderate heat events are due to climate change.
  • Recent extreme heat events expose the dangers and costs of living in a warming world. Exposure to extreme heat is already a significant public health problem and the primary cause of weather-related mortality in the US. A study analyzing the impacts of extreme heat in New York City found that increasing numbers of low- and middle-income households will be exposed to dangerous heat extremes as a consequence of global warming. Another study analyzing heat stress in Rhode Island found that state residents of all ages experience more medical distress when the temperature rises over 75°F. As temperatures continue to increase due to climate change, heat stress is expected to worsen.

For more information on heat waves and 2015 record heat worldwide, see Climate Nexus’ new extreme heat backgrounder.