Climate Impacts

CO2 in the upper atmosphere

418 ppm as of Nov 2023

What's Climate Change?

Climate change is long-term changes in weather patterns resulting from global warming as well as associated impacts.

Visit our Climate Basics page

Impacts of Climate Change

We are already experiencing climate change impacts in Davis and the Sacramento region including an increase in extreme heat days, droughts, poor air quality from wildfire smoke, and rising sea levels in the Delta.

  • The definition of an extreme heat day varies but can generally be described as when temperatures hover 10 degrees or more above an average high.
  • In Davis, an extreme heat day is generally when the temperature reaches 104 degrees Fahrenheit. Source:
  • If human emissions of greenhouse gases continue to rise after 2040, climate models project that Davis will experience an average of 32 extreme heat days per year by 2070compared to just 5 days in 2005.
  • In 2016, the warmest year on record globally, Davis had:
    • 3 extreme heat days—and 14 days over 100 degrees Fahrenheit.
  • California experiences extreme variability in precipitation from year to year, making it prone to both drought and flooding.
  • Climate change will likely make these extreme conditions more severe and frequent—in other words, climate change may make California’s climate even more variable.
  • California’s Mediterranean climate is naturally defined by summer droughts and winter rains—when we get much of our precipitation—so our state has a history of managing water resources for drought.
  • Climate change will most likely increase the frequency and severity of droughts in California—meaning droughts will be hotter, drier, and occur more frequently.
  • Climate change is shifting precipitation patterns in the mountains, increasing the proportion of precipitation that falls as rain and decreasing the proportion that falls as snow.
  • This change in precipitation patterns will drastically reduce snowpack levels in the future, because less snow will fall and snow will melt earlier in the spring.
  • Earlier spring snowmelt will lead to a longer dry season and less water for Californians to use in the summer.

Davis may experience about 55 days at 104 degrees or higher per year on average by 2070.

for Climate Impacts page
  • The Sacramento-San Joaquin Delta is at risk from sea level rise, which is increasing water salinity in the Delta due to the intrusion of salty ocean water.
  • Increases in water salinity in the Delta are reducing agricultural yields and harming native fish.
  • Land subsidencethe sinking of the land surface due to the removal of support under the surfaceis exacerbating risks from sea level rise.
  • Land subsidence is caused by excessive groundwater pumping, which leads to aquifer compaction.
  • Aquifers are spaces in the ground that store large amounts of water—groundwater—so when the water is pumped out, the land compacts and subsides since support from groundwater has been removed.
  • Subsidence can degrade water quality in the Delta because it reduces levee stability.
  • Wildfires in California are becoming more severe and occurring more often–leading to a greater area of burned land.
  • These increases are in part due to longer, more severe droughts associated with climate change.
  • Another driver of increased wildfire activity is the buildup of fuels in many of California’s forests.
    • Historically, these forests experienced natural wildfires often, but fires were normally of low severity.
    • After more than a century of wildfire suppression by humans, many of these forests are denser than they should be, making it more likely that large, severe wildfires will occur.
  • In addition to direct impacts to human life and property, wildfires harm human health by:
    • Reducing healthy air quality
    • Increasing instances of chest pain, respiratory problems, and heart problems
Human Impacts picture for Climate Impacts webpage
  • Climate change will increase economic stress, for example by:
    • Increasing irrigation requirements
    • Increasing electricity demands for cooling
    • Decreasing housing supply
  • Extreme heat days have serious health consequences including:
    • Heat stroke and dehydration
    • Other heat-related illnesses including cardiovascular and respiratory problems, and death
    • An increase in vector-borne diseases
  • Sea-level rise and flooding, as well as other environmental changes associated with climate change, are leading to increasing numbers of climate refugees.
  • Our ability to successfully respond and adapt to these impacts is sometimes referred to as climate resilience.


This graph shows the number of extreme heat days--in Davis, generally when temperature exceeds 103.9 Farenheit--that may occur per year in the future, assuming that greenhouse gas emissions rise through 2050 and peak around 2100 (RCP 8.5 Scenario). This graph uses the CanESM2 climate model, an average simulation of future climate.

Source: Cal-Adapt. Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography); Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder). CanESM2 is one of four models selected by California's Climate Action Team Research Working Group as priority models for research contributing to California's Fourth Climate Change Assessment.


Atmospheric CO2

NOAA Science and Information for a Climate Smart Nation: Climate Change: Atmospheric Carbon Dioxide

NOAA Earth System Research Laboratory Global Monitoring Division, Mauna Loa, Hawaii Observatory: Trends in Atmospheric Carbon Dioxide

Climate Impacts

Human Health

Air Quality

Water Resources

Vegetation and Wildlife

  • US Forest Service Climate Change Resource Center’s Wildlife and Climate Change – information on how climate change is impacting wildlife