Preparing for more summer heat waves

Heat Wave PhotoClimate change is causing longer and hotter heat waves that take a toll on public health and on a community’s economy, prompting some local governments to take action.

Heat can be deadly. From 2006-2010, exposure to extreme heat resulted in 3,332 U.S. deaths. The elderly and the poor are among the most vulnerable due to pre-existing health issues and limited access to air conditioning. But young outdoor enthusiasts are also at risk. Five hikers died during a heat wave this summer in Arizona, where it got as hot as 120 degrees F.

Heat waves are not only dangerous, they’re also expensive. Extreme heat can damage crops and livestock, reduce worker productivity, drive up energy costs, and increase demand for water resources. A 2011 heat wave and associated drought in the Southwest and Southern Plains cost $12.7 billion.

A hotter, drier Southwest

While it’s hard to determine how climate change influences individual extreme weather events, we do know climate change exacerbates both their frequency and intensity.

In the Southwest, residents are expected to see an additional 13 to 28 extremely hot days (temperatures of 95F or hotter) by mid-century, and 33 to 70 additional days by the end of the century. Higher temperatures will also exacerbate droughts and fire cycles.

How to prepare

The Southwest region has already taken steps to prepare for the impacts of more extreme heat. This is especially critical for urban areas, where stretches of heat-absorbing concrete and asphalt create a heat island effect, increasing temperatures in some cities by up to 15 degrees above surrounding areas

In Southern California, the city government in Chula Vista is working to implement 11 strategies to help adapt to the impacts of climate change. They include using reflective or “cool” paving and roofing to reduce the urban heat island effect, and amending building codes to incentivize water reuse and lower demand for imported water.

In Arizona, the city of Phoenix’s Water Resource Plan includes short- and long-term strategies to deal with water shortage scenarios, including monitoring supplies and managing demand, developing increased well capacities for water storage, and coordinating with neighboring counties to secure additional water resources.

A council of local governments in Central New Mexico is working to determine the impacts of heat waves on infrastructure, including the role of extreme heat in degrading asphalt and pavement, and what types of pavement materials are most resilient to extreme heat.

Early efforts to improve climate resilience can help a community prepare for costly extreme weather events and more quickly bounce back from them. Local governments like the cities of Phoenix and Chula Vista and those in New Mexico are demonstrating strong leadership that can be an example for others. Coordinating with partners in state government and the business community, including through the C2ES Solutions Forum, can ensure local governments’ resilience plans provide maximum protection against the heat waves of the future.

Link between extreme weather and climate change comes into focus

Scientists have typically been cautious when discussing the link between a single extreme weather event and climate change, preferring to focus on broader trends. Previous work, including a paper I wrote with Jay Gulledge four years ago, described a framework for how to think about the link.

But a new report from the National Academies of Sciences (NAS) is making the connection more clear by defining the relative contributions of climate change and other natural sources to the risk of individual weather events. The NAS report – an exhaustive, systematic examination of the peer-reviewed literature – finds high confidence in attribution studies linking individual extreme heat and cold events and climate change, and a more moderate confidence level for several other types of events.

Climate change is making extreme weather more likely. But individual weather events like heat waves or hurricanes are always the product of several risk factors, such as El Nino, climate change or other natural variability, akin to how a poor diet and smoking increase the risk of poor health later in life.

Extreme event attribution attempts to quantify the influence of climate change in comparison to other factors. Determining to what extent climate change strengthened or weakened the event can further our understanding of how much impact climate change is having on our weather.The NAS report assigns a confidence level to the climate impact for a variety of weather events based on three supporting lines of evidence:

  • The physical mechanisms that link climate change to a particular extreme
  • The length and quality of the observational record showing the baseline risk level and changes to date
  • Computational climate modeling showing an increase in risk for a class of extreme event

The report finds the strongest links to climate change for extreme heat and cold, with the highest level of confidence across all three lines of evidence. Drought and extreme rainfall have medium confidence for physical understanding, observation and modeling. Extreme snowfall has medium conference for two out of three, physical understanding and modeling, while the observational record for snowfall is poor.

2015 was the warmest year on record

Image courtesy NOAA

This visualization from NOAA shows much warmer than average or record warm temperatures across much of the globe in 2015, the warmest year on record.

The data are in, and 2015 was officially the warmest year globally ever recorded. We’ve been keeping temperature records since 1880. The last time the record was broken? 2014.

What’s interesting is just how much warmer 2015 was. The observed annual average surface temperature was more than 1.8° F (1° C) above the 19th century average, according to the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA). That’s already half the warming countries have agreed to as the international limit.

And 2015 was about a quarter of a degree Fahrenheit warmer than 2014. That might seem small, but it’s actually huge when compared to the year-to-year differences observed in the record.

A strong El Niño, when the surface ocean in the Eastern Pacific basin warms, contributed to the record warmth of 2015. But even compared to other El Niño years, 2015 set records. The agencies reporting the data attribute this to the long-term warming trend due to the increase of greenhouse gases in the atmosphere.

As with all climate and weather data, the 2015 data shows some variability. Not all locations set high temperature records, and parts of the North Atlantic Ocean actually set a cold temperature record.

In the contiguous United States, 2015 was the second warmest year on record, with 2012 still holding the top spot. It was the 19th consecutive year that the annual average U.S. temperature was more than the 20th century average.

Extreme Weather and Resilience: An Ounce of Prevention

A recent Senate hearing highlighted some of the progress U.S. communities are making, and the major challenges they face, in better coping with costly extreme weather events — including those, such as heat waves and coastal flooding, whose risks are heightened by climate change.

Sen. Tom Carper, chairman of the Homeland Security and Governmental Affairs Committee, noted that the “frequency and intensity of these extreme weather events are costing our country a lot - not just in lives impacted – but in economic costs, as well.” Nearly 130 weather-related events in 2013 caused more than $20 billion in losses in the United States.

Extreme weather is costly, not only to federal, state, and local governments, but also to businesses and individuals.

Much of the Senate testimony echoed key findings in our report, “Weathering the Storm, Building Business Resilience to Climate Change.”  Three key points made at the hearing were:

The State of the Climate

As President Barack Obama prepares to deliver his State of the Union address, we believe it’s a good time to take a look at the state of our climate: the growing impacts of climate change, recent progress in reducing U.S. emissions, and further steps we can take to protect the climate and ourselves.

The consequences of rising emissions are serious. The U.S. average temperature has increased by about 1.5°F since 1895 with 80 percent of this increase occurring since 1980, according to the draft National Climate Assessment. Greenhouse gases could raise temperatures 2° to 4°F in most areas of the United States over the next few decades, bringing significant changes to local climates and ecosystems.