Sustainability, Energy and Environment Community

University of Colorado Boulder


The impacts of climate change will be devastating if we do not take action.

Almost everyone knows that the world is warming up. The U.S. has warmed by 1.8°F since the beginning of the industrial revolution, and is projected to warm by a total of 3 to 7°F by the end of this century, if we act quickly, and 6-12°F if we don't (NCA4 CSSR report, IPCC report SR15).

Our entire society has been built around the climate that we expect – in other words the climate of the recent past. Many of our cities are built right on the shoreline – or where the shoreline has been for the last several thousand years. Cities and infrastructure are designed to withstand weather and floods based on past experience. Crops are planted where the weather has suited them and water was available.

So when our climate changes, it impacts so much of the world around us. The magnitude of the impacts will vary depending on how aggressive we are in tackling climate change.

Moreover, an increasing global population drives up energy use and emissions across the board, putting further pressure on stressed climate systems and related ecosystem services.

Warmer temperatures

Temperatures will go up everywhere, but in some places they will rise more than others – including the Northern Hemisphere and United States. Most people also don’t realize that over 90% of the extra heat that the earth is absorbing is going into the oceans, not the air, so the oceans are also heating up. This impacts sea level rise, coral growth and hurricane intensity. Heat waves in the summer will become more intense and this will be a major problem for areas like Florida, Texas and the Southwest that are already very hot.

Higher sea level

Sea level rise is potentially one of the most damaging aspects of climate change. Average sea level is projected to increase about 3 feet by 2100, but the latest research shows there is the potential for much larger increases due to potential ice sheet instability (Science article). Coastal cities are already experiencing much more “sunny day” flooding at high tides due to sea level rise, and this will only get much worse. Millions of people and billions of dollars of infrastructure lie within a few feet of sea level. The Chief Economist of Freddie Mac estimates that the financial impact from rising sea level may very well exceed the impact of the housing and financial crisis of 2008.

Warmer, more acidic oceans

Increased ocean temperatures are projected to result in increased coral bleaching, like that observed in the Great Barrier Reef in 2016 and 2017. Since coral reefs serve as the nurseries for many fish, the downstream impacts could be severe. The sea is also absorbing some of the CO2 that is being produced, and this is making the oceans more acidic. Oyster farming in the Northwest has already been impacted as the acidic ocean water negatively impacts oyster shell growth. Recent research also shows that cod stocks could decline by 75% or more by the end of the century due to ocean acidification (BBC article).

More intense weather

Increased temperature leads to more evaporation as well as more moisture storage capacity in the air. Droughts will be especially damaging in the already dry Southwest, and have already been linked to the recent increase seen in forest wildfires. Some areas will experience more intense precipitation events as a result of the greater moisture storage capacity of the warmer air. Hurricane intensity is projected to increase along with the warming ocean. It is unclear at this time if the amount of hurricanes each season will increase.

Stress on human health

Extreme heat waves are the current leading cause of weather-related deaths in the U.S. (The National Climate Assessment, 2014 Report). As temperatures increase, summer heat waves will become even hotter and longer. Air quality is likely to decrease due to wildfires and other issues. Higher temperatures also favor the spread of diseases that are limited by cold (EPA website). Extreme weather events, and the threat of climate change itself, can place stress on mental health.

Humans have an amazing ability to adapt to their environment, and we will have to adapt to future changes that we have already "locked in". But if we are not proactive enough, the changes that we trigger in our environment could be faster than we can adapt to, causing major disruptions in society.

Learn More

For those who want a more detailed description of the impacts across the U.S., see the Fourth National Climate Assessment (Vol. II). Chapters 18 – 27 show impacts for 10 regions:

Northeast    Southeast    U.S. Caribbean    Midwest    Northern Great Plains    Southern Great Plains    Northwest    Southwest    Alaska    Hawai‘i & U.S.‑Affiliated Pacific Islands   

Map of 10 U.S. regions for the National Climate Assessment

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