Climate Change Poster
California’s Climate Water Connection
California’s Mediterranean climate directly impacts the water resources that millions of people rely on. Seasonal and annual variability in precipitation with long, dry summers, and dramatic swings between flood and drought, along with an imbalance between where the water falls and where the people live, have made water management a challenge for over a century.
Climate change brings new challenges for managing California’s water resources. Rising sea levels, record-breaking high temperatures, and a reduction of the Sierra snowpack are just a few impacts we are already seeing. Scientists expect climate change will have a growing impact on our resources in the coming years.
To responsibly manage our water resources, Californians need to understand why climate change is happening, how it will impact our state’s water resources, and what we can do to adapt to and mitigate the changes.
The sections of text below correspond to keys identified in DWR’s “Climate Change and the Future of California’s Water” poster. Click below to dig deeper into climate science and how a changing climate affects one of our most important natural resources.
Carbon dioxide (CO2) is an essential part of life on Earth. If it weren’t for CO2 in our atmosphere, Earth would be much colder than it is right now, at an average of -.4 degrees Fahrenheit (-18 degrees Centigrade) instead of the current average of 58F (15C).
Our food chains also rely on CO2. Plants require it for photosynthesis. Animals then eat plants, which moves the carbon through the food chain. Carbon is then re-released into the atmosphere or oceans as CO2 respiration, decomposition, and other natural processes. While some carbon continues to move through this cycle, over millennia other carbon is converted into rocks such as limestone and “fossil fuels,” like coal, oil, and gas. The carbon cycle has held fairly steady for at least the last half million years with atmospheric CO2 concentrations ranging between 180 and 300 parts per million.
This changed about 200 years ago with the onset of the Industrial Revolution. As people began to extract and burn large quantities of long-buried carbon – first in the form of coal, later as oil and gas – to power our factories, cities, homes, and vehicles, the carbon cycle was knocked off balance. As people burned these fossil fuels for energy, tons of carbon dioxide were released into the atmosphere and our oceans.
As a result of industrialization, atmospheric CO2 levels now stand at more than 400 parts per million, levels not seen since the Pliocene epoch when global average temperatures were 2 to 3 degrees C (3 to 5 degrees F) warmer than today and the sea level was 82 feet higher.
Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are primarily due to increased levels of atmospheric carbon dioxide resulting from burning fossils fuels. Scientists reach these conclusions by studying real-time data, such as atmospheric CO2 levels and composition and temperature records. Using this data, scientists also develop climate models to project different scenarios.
Climate models are computer programs that use mathematical equations to represent the processes and interactions that drive the Earth’s climate. There is no single climate model – climate scientists use many simulations from multiple models to investigate different scenarios and a range of possible future variations and changes. As scientists learn more and computers become more powerful, the models become increasingly precise. Today, virtually all models indicate that temperatures are rising due to human activity and that we can expect significant planet-wide warming in the coming decades.
Melting mountain snow provides much of California with water during the hot summer months. People living in rural communities and cities, farmers, and fish and other wildlife all rely on this steady supply of cool runoff. Rising temperatures threaten the year-round availability of water for much of the state.
Over 27 million Californians depend on water that originates in the Sierra Nevada.
Snowpack, snow water content, and runoff from the Sierra Nevada have all declined in the past 50 to 100 years.
During the 2011-2015 California drought, human-caused warming reduced the snowpack by 25 percent. Even in the record breaking water year of 2016-17, the snowpack levels were 20 percent lower than they would have been with no human-caused warming.
As CO2 levels increase in the atmosphere, so does its ability to trap heat from the sun. In the last 100 years, the average global temperature has risen at an unprecedented rate. Drought, forest fires, decreased snowpack, and more frequent and intense heat waves are just a few of the consequences of higher temperatures.
- Since the late 19th century, the global temperature has risen 1.62 degrees Fahrenheit (0.9 degrees Celsius).
- The 20 hottest years on record occurred between 1995 and 2018, with the five warmest years occurring since 2010.
- In California, average temperatures rose nearly 2 degrees Fahrenheit during the second half of the 20th century. Without reducing heat-trapping gas emissions, they could rise an additional 8.8 degrees Fahrenheit by 2100.
- Although California’s 2011-2016 drought was caused by low precipitation, higher temperatures intensified its impacts.
- In 2015, the lack of below-freezing temperatures led to the smallest snowpack on record in California.Higher temperatures lead to a loss of soil moisture, which exacerbates droughts and increases the size and severity of wildland fires.
- Heat waves, such as the one in 2006 in California and those in Europe in 2003, 2010, and 2018, lead to increased heat-associated deaths and illnesses.
- Warmer air can hold more water, raising the likelihood of flooding from large storms caused by atmospheric rivers.
To slow the rate of climate change, we all need to do our part. The best way to take action is to join with others – friends, family, classmates, or neighbors. Working together is the key to protecting our future.
See the external resources below for additional information:
Project Drawdown is a comprehensive plan of the 100 most substantive, existing solutions to address climate change by rolling back global greenhouse gas emissions.
California Legislation, Regulations, and Executive Orders provides links to laws enacted by the Governor and Legislature to put California on the course of reducing greenhouse gas emissions while addressing the impacts on the state of a changing climate.
Talking about Climate Change is a 17-minute talk by noted climatologist Katherine Hayhoe focusing on how and why to talk about climate change and highlighting the many actions we can take to reduce carbon emissions.
Climate Interpreter Solutions provides links to a variety of resources that focus on community level solutions currently being implemented across the United States.
Adaptation – Adjustments in how we live, such as improving water efficiency and siting new development outside of undeveloped floodplains, that will help lessen the impacts of climate change.
Atmosphere – The blanket of gases surrounding the Earth that contains the air that we breathe and also warms the planet by day and cools it at night.
Carbon Dioxide (CO2) – A gas comprised of one carbon and two oxygen atoms. A minor but very important component of the atmosphere, and a very effective heat-trapping gas.
Climate - Average weather for a particular region and time period, usually measured over at least 30 years.
Climate Change - A change in global or regional climate patterns. Used primarily to refer to changes that became apparent in the mid-to-late-20th century and attributed largely to the increased levels of atmospheric carbon dioxide produced by human activity, primarily the use of fossil fuels. Sometimes called anthropogenic (human-caused) climate change to differentiate from climate change that occurred in the geologic past.
Mitigation – Actions, such as increasing automobile fuel efficiency standards or switching from coal-fired power plants to solar energy, taken to limit the magnitude or rate of climate change.
Weather – Conditions experienced outside over a short period of time. For example, a sunny day, a rainy day, a three-day blizzard, or week-long heat wave are all weather conditions, rather than climate conditions.