Climate Change in Colorado


“Climate is what you expect, weather is what you get” – Mark Twain

First off, what is climate? Weather is the short term changes we see in temperature, clouds, rainfall, humidity and wind in an area.  The climate of a region is when we take the weather and average it over many years. “Climate Change” refers to any long-term change in earth’s climate, or the climate of a region or city. This includes changes besides just temperature.

Is the earth’s climate changing?

The earth’s climate is always changing and it always has been.  The earth cycles between warmer and cooler periods, which last for thousands of years.   So why are we so concerned with “Climate Change”?  

Scientists have made observations which show that the Earth’s climate has been warming.  Over the past 100 years the average temperature has risen a little more than one degree Fahrenheit.  

But it is only one degree!  While this amount may not seem like much small changes in the earth’s average temperature can lead to BIG impacts.   

Climate Change Basics

Climate Change 101 with Bill Nye


As you may have heard, some of the causes of climate change are natural.  These include changes in Earth’s orbit, the amount of energy coming from the sun, ocean changes, and volcanic eruptions.  But most scientists agree this does not and cannot account for the recent increases in temperature.  Since the mid-1900’s scientists believe we have impacted the earth by deforestation and the burning of coal, oil and gas.  This adds heat-trapped gases such as carbon dioxide, methane and nitrous oxide into the air.  These gases are what we call ‘greenhouse gases.’

CO2 levels throughout history (Source: Scripps Oceanography Institute)


There is no doubt Colorado’s climate is changing.  According to multiple independent measurements, Colorado temperatures have increased by approximately two degrees (F) between 1977 and 2006. You may be asking, it is only two degrees what effect does this really have?  It turns out a pretty large one.

Colorado Temperature Trends 1900-2012 (source: Colorado Health Institute)


Changes in temperature and precipitation are affecting Colorado’s snowpack or the amount of snow that accumulates on the ground.  The snowpack has decreased since the 1950s in most of the Western United States, due to earlier melting and less precipitation falling as snow.  In fact, the amount of snowpack measured in April has declined by 20 to 60 percent at most monitoring sites in Colorado. Scientists predict that snowpack in the Southern Rockies will drop 50% this century and the Sierra Nevada snowpack is expected to decrease by 90%.  

This diminishing snowpack can shorten the ski season along with other forms of winter tourism and recreation.  Basically, the earlier melting means that spring starts a little sooner and summer lasts a little longer every year.  

Scientists predict that snowpack in the Southern Rockies will drop 50% this century and the Sierra Nevada snowpack is expected to decrease by 90%.  Less snow also means less water…

Click here to see a time lapse video of changing snowpack

Water Supply

The Colorado Climate Report is a synthesis of climate change science important for Colorado’s water supply.  A summary of findings in this report suggests that there will be a reduction in total water supply by the mid-21st century.  These changes in quantity of water could occur due to warming even in the absence of precipitation changes.

As mentioned earlier, climate change is affecting the Colorado snowpack.  We receive 70% of our water from the snow so less snow means less water.  


Higher temperatures and drought are likely to increase the severity, frequency and the extent of wildfires in Colorado.  These wildfires have the potential to cause destruction to property, livelihoods, and human health.  The smoke created by wildfires can reduce air quality and increase medical visits for chest pains, respiratory problems, and heart problems.  Since 1985, the size and number of western forest fires have increased significantly.

A wildfire tears through a neighborhood in the hills above Colorado Springs (Source: Denver Post)

Changing Ecosystems

The diminishing snowpack allows subalpine fir and other high-altitude trees to grow at higher elevation.  But aren’t more trees a good thing?  The upward movement of the tree line decreases the extent of alpine tundra, which fragments these ecosystems, possibly causing the loss of some species (EPA).  

If you have been to the mountains recently there is no doubt that you have seen the devastation caused by the pine beetles, which have killed over 3.4 million acres of trees in Colorado.  Rising temperatures and fewer below freezing winter days allow them to live successfully at higher elevation.  These dry, dead trees increase the likelihood of large forest fires.  This causes authorities to be forced to limit access to hiking and camping affecting Colorado’s tourism and economy.  

Effects of the pin-bark beetles near Granby (Source: Denver Post)

Rising water temperature and the changing chemistries of Colorado’s alpine lakes and streams make it harder for trout amphibians, water bugs and aquatic plants to survive. Their decline will result in a destabilization of entire ecosystems.  

Large mammals are affected due to changes in their food source caused by warming temperatures.  Large Rocky Mountain mammals are being forced to higher elevations.  These rising temperatures also bring deadly parasites and disease to these higher altitudes, which further reduce their populations (Western Association of Fish and Wildlife Agencies, 2007).

In the high Rockies, snow melt date initiates the plant growing season.  The earlier snowmelt date causes earlier flowering in species like the glacier lily.  These changes in wildflowers may change resource availability for pollinators like birds and insects and herbivores that depend on them for food.

What does the IPCC Special Report on 1.5C global warming actually mean?

How does the latest National Climate Assessment fit in? What to make of recent headlines that CO2 emissions are at an all-time high? What about permafrost melting? Feedback loops? What does it all mean? Professor Scott Denning explains recent news reports, and relates them to state and local climate action plans.  Professor Denning is a professor of atmospheric science at Colorado State University in Fort Collins. He spoke by invitation of the Denver chapter of 350 Colorado. A condensed version of his talk is at




Colorado Health Institute

Colorado Climate Report