A new analysis shows surface waters are warming along all U.S. coastlines and in each of the Great Lakes, as well as in many freshwater streams. Warming waters harm fish, their ecosystems, and the local economies that depend upon them.


  • The data shows the average surface water of each Great Lake has warmed by at least 1.5 degrees since 1995.
  • Nearly two-thirds of rivers and streams with reliable data are warming.
  • All U.S. coastal surface waters have warmed since 1901; research suggests the oceans are heating substantially faster than previously estimated.
  • Details below — and read our related report.


  • Pollution from fossil fuels, deforestation and other sources traps heat, raising air temperatures as well as water temperatures. An associated shrinking of snowpacks and earlier melting seasons further warm rivers and streams. Intensifying rainfall from climate change worsens water pollution.
  • Fish can only withstand particular temperature ranges. As waters warm, they face increased disease threats, and their populations seek cooler waters by shifting northward, into deeper waters, or higher in elevation. They face local extinction threats when they can travel no further. Algae blooms that can kill fish and ruin fishing trips occur more frequently as temperatures rise.
  • An estimated 36 million Americans fish each year, spending $46 billion on an industry that’s being threatened by warming. When it comes to commercial fishing, fleets are burning more fuel and spending more hours on the water as they venture farther out to sea in pursuit of fish that used to thrive locally.


Some ideas for questions to ask when producing a local story about warming water: Are temperature changes affecting fish stocks or fishing? Are they linked to local algae outbreaks? Have fishing restrictions been imposed recently — if so, why? Are steps being taken to protect water quality? How would future warming affect fishing and the economy?



  • Fishing clubs, marina operators, recreational fishers, riverkeepers and baykeepers and others with strong connections to the water. Have they noticed any changes? How are they affected? Can you join them for some field reporting?
  • Local elected officials and city and county staff. Are they concerned about local water quality? Are they taking steps to protect it?
  • State officials, including environmental protection and fish and game staff. What’s the state doing to protect water quality? Has the state studied impacts from warming waters? Is it taking steps to address climate change?
  • NOAA’s Sea Grant extension officesGreat Lakes Environmental Research Laboratory, and National Centers for Environmental Information, local and state USGS centers, local watershed centers.
  • Local researchers and scientists. Experts can be sought through local universities and by reaching out to groups that connect scientists with journalists, such as SciLine500 Women Scientists and the Climate Science Rapid Response Team.

METHODOLOGY: Climate Central analyzed USGS river and stream gauge temperature data, analyzed NOAA ocean temperature data, and obtained Great Lakes temperature data from NOAA. The full methodology is spelled out in our report.

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