Extreme Heat Poses Serious Immediate and Long-Term Health and Adaptation Challenges

Communities throughout the world this summer are facing new, and in some respects unprecedented, challenges with extreme heat. According to the World Meteorological Organization, the planet just experienced its hottest week on record from July 2nd through the 9th. Local records for heat exposure are buckling across the planet, from Phoenix, Arizona, and Miami, Florida, both of which are experiencing their longest streaks of consecutive record high temperatures, to Italy and Spain, parts of Africa, the Middle East, China, and India, which in some areas are seeing daily heat indexes rise above 50C (122F).

While health impacts from heat include dehydration and heat stroke, increasing infectious disease transmission, and respiratory stress, other social impacts include loss of working hours and productivity, sleep disruption, and instability of basic infrastructure like power and water.

Often the most adversely affected communities from extreme heat waves are those already living in tropical areas, which are disproportionately poor and contribute little or nothing to greenhouse gas emissions. However, many historically colder areas of the world, from the Pacific Northwest in North America to the United Kingdom and Ireland, parts of Scandinavia, Switzerland, and Austria, are also experiencing their own crises of adaptation, often based on the pervasiveness of infrastructure that was originally developed for much lower average and minimum temperatures and which now often fails to offset increasing heat.

The combination of high El Nino marine temperatures in the Pacific and long-term climate patterns as the world nears the +1.5C threshold set by the Intergovernmental Panel on Climate Change (IPCC) for “safe” levels of global warming appear to be principally driving the recent spikes in temperature. What does the future hold for these types of trends, if climate forecasts worsen beyond 1.5C, as many scientists expect will happen within only a few more years, both for areas already experiencing extreme heat and for those facing relative adaptation crises?

New modeling from researchers at Oxford University, published this week in the journal Nature Sustainability, makes a case that we can expect drastic changes in heat exposure in both absolute and relative terms, throughout the world. Moreover, those changes imply very different scenarios and policy implications, depending on whether the increases are occurring absolutely or relatively, in areas already acclimated to heat or more historically temperate.

Using the standard metric of the “cooling degree day,” or CDD, which measures heating above a temperate standard of 18C (65F), the researchers conclude that large parts of the tropics will see massive increases in exposure to elevated heat, requiring improved access to cooling. Countries like the Central African Republic, South Sudan, Chad, and Uganda will see increases in CDDs of more than 220 annually, dramatically worsening anticipated health impacts and loss of livelihoods based on pre-existing lack of access to affordable cooling. Meanwhile, countries like Switzerland, the UK, Sweden, and Denmark will see proportional changes in annual CDDs of more than 24%, placing enormous strains on public and private budgets to equitably shift their infrastructures towards increasing cooling capacity over the short- and medium-term.

Direct Relief’s global humanitarian distribution network already serves a large proportion of people in areas experiencing high degrees of heat stress, with many of them likely, according to this new research, to face even greater impacts as the world moves further towards a 2C warming scenario. Based on the Oxford team’s calculations, on average, Direct Relief’s recipient network is expected to see an additional 132 cooling degree days under the 2C scenario. Additionally, the 579 organizations in Direct Relief’s network at the upper end of the absolute warming increases beyond 1 standard deviation from the mean, are expected to see average increases of 209 CDDs, a 37% increase over the network average.

In terms of relative increases, the Direct Relief network is expected to see an average increase in CDDs of 12.9%. Organizations seeing changes at 1 standard deviation above the mean are anticipated to experience increases in CDDs ranging from 19% to 108% under the 2C scenario. Organizations in the Direct Relief network expected to see these large relative changes tend to be located in California, the U.S. Midwest and Northeast.