Climate Change & Regional Planning

How is Our Climate Changing?

The Climate Change Sixth Assessment Report, states that the past five years (2016-2020) have been the hottest 5-year period since at least 1850. The hottest five years on record in San Diego have also been the past five (see the Increasing Temperature section below). That is, the San Diego region's climate, like all others, is changing, and threatening our quality of life and economic prosperity. 

By the end of the 21st century, the temperature is predicted to increase in San Diego County by more than 5˚F to as much as 10˚F, in large part due to anthropogenic emissions of greenhouse gases, with the increase depending on the GHG emissions in the near-term. In addition to increasing temperature, our region will experience more frequent and more intense heat waves. Precipitation patterns will change to become more extreme, with wetter winters, drier springs, more frequent and more severe droughts. During this same time an increased risk of wildfires, declines in native plant and animal populations are also anticipated.

Increasing Temperatures

Due largely to the globally increasing temperatures, ocean thermal expansion coupled with melting ice is expected to raise the sea level along the San Diego coast by one (1) foot in 2050 with an increase to at least three (3) feet in 2100, even though regional nuances are also expected.

Sea Level Rise

Sea level rise will exacerbate the effects of extreme high tides through more frequent coastal flooding, which we already experience. Along the West Coast of California, the frequency of high tide flooding has remained nearly constant except for a few locations. In the San Diego region from 2000 to 2015, the frequency of high tide flooding increased from 25% to 50% in the San Diego Bay and La Jolla areas which is explained primarily by regional sea level change. This effect may be compounded if it coincides with El Nino events. By 2050, high tide flooding in these areas of the Southwest Pacific is expected to occur 15 to 35 days per year, and by 2100, coastal flooding is expected to occur 345 days per year under a medium level of emissions. The ultimate long-term regional sea level rise will depend on the measures taken to mitigate greenhouse gas (GHG) emissions locally and globally, with resulting temperature change.

Human Contributions: Greenhouse Gas Emissions

The future magnitude of the increase in climate impacts will depend on how much greenhouse gas emissions are emitted in the future. It is critically important to reduce GHGs to minimize additional impacts on future generations.

In California, GHG emissions have generally decreased during the 2000-2019 period, due to state mandates with a target for 2020.

Accelerating GHG emissions [link to:] from human activities contribute to climate change impacts. The main greenhouse gases (GHGs) included in community-wide GHG analysis are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).


The transportation sector is the largest contributor of greenhouse gas (GHG) emissions in California. In 2019, direct emissions from vehicle tailpipes, off-road transportation mobile sources, aviation, rail, and watercraft accounted for 40% of statewide emissions. This pattern is similar in the San Diego region and in its cities. From 2015 to 2018, emissions from vehicle tailpipes alone contributed 54% to 56% of total emissions each year within the City of San Diego, even as the total emissions have decreased 5% since 2015. Building energy usage, such as lighting and appliance electricity usage, and heating and cooling natural gas usage contributes the second largest source of GHG emissions, with over 40% annually. Other GHG emissions arise from solid waste disposal, wastewater processing and from energy to convey, treat and distribute water to drinking levels.

While meeting the 2020 target was relatively painless for California and the San Diego region and its cities, it will be more challenging to meet the 2030 targets set by the State to reach 40% below 1990, let alone to be carbon neutral in the timeframe 2045-2050. Globally, and collectively, countries are not on track to meet the Paris Agreement climate change targets of achieving close to carbon neutrality by 2050.

How Are We Planning and Responding?

Planning GHG Mitigation

GHG mitigation planning is well underway in our region through Climate Action Plans. Eighteen (18) out of nineteen (19) jurisdictions in the region have adopted Climate Action Plans (CAP). Some of which are aspirational, but the majority have legally binding GHG targets within the context of the California Environmental Quality Act.  

At the regional level, the San Diego Association of Governments (SANDAG) prepares and updates a Regional Plan every four years, which contains several elements that intersect with climate planning. For example, its Sustainable Communities Strategy is an element in the Regional Plan that is required by state law, to show how development patterns and transportation systems will work together to reduce GHG emissions from passenger vehicles. The latest draft Regional Plan 2021, shows a long-term blueprint for a lower carbon sustainable future for the San Diego region. 

It is the successful implementation of measures, and achievement of the GHG targets, that will determine the GHG emissions in future. From 2015 to 2021, SANDAG took the lead in bringing together the jurisdictions to ensure consistent and quality GHG assessment and tracking. Consistent methodologies using best available data were developed, and a Climate Action Data Portal was developed to publicize the GHG inventories, providing activity data and indicators to be tracked on an annual basis.

To better communicate progress, in 2020, the San Diego Regional Climate Collaborative released an ESRI Storymap, synthesizing data from CAPs and information from Climate Collaborative member entities that highlight the nexus between CAP GHG measures and local projects as well as regional climate leadership.

Planning and Adapting to Climate Change Impacts

Climate change adaptation can be defined as the adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. In 2018, the Climate Collaborative prepared The Regional Adaptation Needs Assessment to assess how local jurisdictions are addressing climate adaptation by either integrating into existing plans, such as General Plans or Hazard Mitigation Plans, or by developing separate Adaptation Plans. 

While adaptation planning lags efforts for GHG mitigation, in recent years, many regional and local agencies have increased their planning efforts to address climate adaptation, helped jurisdictions address climate resilience planning more holistically, and integrated across multiple planning efforts to streamline success. The California Office of Research and Planning defines resilience as the capacity of any entity – an individual, a community, an organization, or a natural system – to prepare for disruptions, to recover from shocks and stresses, and to adapt and grow from a disruptive experience. 

Recently, hazard mitigation planning and climate change adaptation planning are being integrated. For example, in 2017, the San Diego County Multi-Jurisdictional Hazard Mitigation Plan was updated to include climate change as a hazard that will exacerbate existing hazards. In particular, Sea Level Rise, Coastal Storms and Coastal Erosion, with up to two feet of sea level rise by 2050, have been mapped and particularly vulnerable communities identified within hazard mitigation plans. With projected higher temperatures and reduced rainfall, wildfire, drought and water supply are expected to affect the San Diego region’s cities, agriculture, and ecosystems. Potential exposure to every hazard has been identified for each jurisdiction within San Diego County and losses from the 100-Year and 500-Year Flood Hazards and Critical Facilities and Infrastructure losses from the 100-Year and 500-Year Flood Hazards have been mapped.

Another example of an on-going regional adaptation effort spearheaded by SANDAG and Caltrans is the Holistic Integration of Adaptation and Transportation Resilience Strategies (HIATRS) project which is developing guidance for economic and equity analysis for adaptation strategies. 

More specific vulnerability assessments (VA) are still relatively rare. In 2017, the City of Del Mar, and the City of Carlsbad completed a vulnerability assessment for coastal risks. Other entities which have carried out VAs are Caltrans SD Region 11 and DOD for Naval Base Coronado and Marine Corps Base Camp Pendleton. The City of San Diego developed a draft Sea Level Rise VA in 2019. 

As part of improved adaptation and resilience practice, California has now recognized the value of prescribed burns, a practice common to pre-European peoples, to reduce the incidence of catastrophic fires. The California Forest Carbon Plan 2018 estimates that over 4.5 million acres burned annually in California prior to European settlement, including fires started or managed by indigenous peoples, and thereby avoided the catastrophic fires we see today. In 2018 an average of 17,500 acres/year were burned in prescribed fire, much less than that of the pre-European amounts. The goal is to increase these prescribed burns to 60,000 acres/year by 2030. Regionally, the County of San Diego developed a Resilience Program in 2019 for its unincorporated areas, including the Wildland Fires Resilience Review Report, which outlines strategic initiatives to best prepare, respond to, and recover from wildland fires. 

San Diego Gas & Electric (SDG&E) also released a Wildfire Mitigation Plan in early 2020 based on lessons learned from the catastrophic fires of 2003 and 2007 and because several of those fires were caused by sparks emanating from the electricity grid system. SDG&E built a dense, utility‐owned network of 220 weather stations to provide detailed 10-minute weather data and wind speed reporting every 30 seconds across its service territory. Based on this data, SDG&E has begun de‐energizing areas of the grid upon reception of dangerous fire weather conditions. 

For extreme heat adaptation, the County of San Diego together with SDG&E opened seven (7) Cool Zones to the public in June of 2021.

Other long-term adaptation and resilience efforts include combating urban heat islands and increasing urban tree canopy cover as described in Groundwork San Diego’s storymap.

What Are We Measuring?

To estimate the human contributions on climate, we measure the greenhouse gas emissions from cities in the San Diego region.