Houston Climate Impact Assessment 2.0

Houston’s  Climate Impact Assessment  helps us understand the local heat, drought, and precipitation risks associated with climate change (climate risks) while also demonstrating the importance of reducing and capturing emissions of carbon dioxide, methane, and other greenhouse gases (GHGs).

By comparing historical climate observations from 1950, the assessment report looks at how future temperature and precipitation is expected to change across the greater Houston region through 2100.

The climate change projections are based on two scenarios representing lower and higher GHG emissions (RCP4.5 and RCP8.5) resulting from human activities.

Impacts are assessed using a series of indicators, which include estimated likelihood and frequency of high intensity events (e.g. droughts, heavy rainfall, and heat waves) as well as more chronic stressors (e.g. annual average temperature, number of hot days with temperature above 100°F, number of warm nights with temperature above 80°F, etc.).

The Climate Impact Assessment is also complementary to the  City of Houston's Hazard Mitigation Plan 2018 Update , which identified 12 natural hazards based on a risk assessment and review of mitigation actions. The Plan update addressed similar climate impacts, including: Extreme Heat, Hurricane, Winter Storm, Drought, Flood, Wildfire, and Expansive Soils.

•  Climate Impact Assessment  (2020): The study was conducted by Drs. Anne Stoner and Katharine Hayhoe of  ATMOS Research & Consulting  and is based on recent data, using a combination of global and regional climate models, statistical downscaling and expert judgment (including interviews with key city officials and researchers). For more information on data sources and methodology, please refer to the assessment report.
• Additional data sources are linked throughout the narrative.

Adaptive Capacity: A system’s (e.g., communities, institutions, public services) ability to reduce hazardous exposure and cope with the health consequences resulting from the exposure (Definition from CDC.gov) 

Climate risk: Hazards associated with changes and variability in long-term climate, such as temperature and precipitation extremes, that impact populations, physical facilities, production processes, markets, and supply chains

Cooling Degree-Days (CDDs): The number of degrees that a day’s average temperature reaches above 65º F; Used to quantify the energy demand needed to cool a building on a hot day

Carbon dioxide equivalent (CO2e): Standard unit for reporting GHG concentrations

Greenhouse gases (GHGs): Heat-trapping gases in the atmosphere, primarily carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6)

Representative Concentration Pathway 4.5 (RCP4.5): A lower scenario where GHG concentrations reach 580 parts per million (ppm) by the year 2100; Represents a future where the majority of the world follows the stated goal of the city of Houston to meet its Paris Agreement targets, transitioning to clean energy sources and reducing carbon emissions

Representative Concentration Pathway 8.5 (RCP8.5): A higher scenario where GHG concentrations reach more than 1200 parts per million (ppm) by the year 2100; Represents a future where fossil fuel use and carbon emissions continue to increase through the end of the century, tracking historical trends to date

Houston has grown to  667 square miles in 175 years  and is divided into 88 Super Neighborhoods. The nine-county metropolitan area contains 157 cities and Census Designated Places, and rapid growth of the Greater Houston region is increasing developed land area. 

According to the American Community Survey, Houston’s population is  49.9% male and 50.1% female . Houston is a young city. The median age is  33 male years ,  25.1%  of the population is under 18, and  10.5%  of the population is over 65. Life expectancy in Harris County ranges from  78.5 to 82.5 years  on average, with the highest life expectancy in west Houston and north Harris County and the lowest life expectancy in northeast Houston. 

Many immigrants call Houston home ( 29.3% of the city's population ). Most foreign-born Houstonians come from  Latin America or Asia ,  72%  of them entered the U.S. before 2010, and  31%  of them are naturalized citizens. Median household income is  $52,338 . In 2017, the median annual income of households in Houston was approximately  15% less  than median annual household incomes across Harris County, the state, and the nation . The unemployment rate Is  5.9% , above the state average of 5.1%. The mean travel time to work is  27.7 minutes , and  77.7%  of the population drives alone to work. Houstonians are more likely than the average Texan to use public transportation or walk to get to work ( 5.7%  compared to the statewide average of 2.9%).

The median household income is  $52,338 . In 2017, the median annual income of households in Houston was approximately  15% less  than median annual household incomes across Harris County, the state, and the nation . The unemployment rate Is  5.9% , above the state average of 5.1%. The mean travel time to work is  27.7 minutes , and  77.7%  of the population drives alone to work. Houstonians are more likely than the average Texan to use public transportation or walk to get to work ( 5.7%  compared to the statewide average of 2.9%).

Houston is currently the fourth largest city in the country, with a population of  2,325,502  and growing. The nine-county metropolitan area is home to  6,997,384  people. By 2040, there may be one million more Houstonians and  four million more residents in the region .

Houston is one of the most  racially diverse  places in the country, growing more diverse each year: the city is 44% Hispanic, 25% Non-Hispanic White, 23% Black, and 7% Asian. However, large parts of the city remain racially segregated. Between 2010 and 2030, Houston's Hispanic and Black populations are expected to  grow 60% and 34% , respectively, compared to a 4% increase in Houston's white population. By 2040, the region is expected to create an additional  1.5 million jobs  (compared to 2.7 million jobs in 2010) and the statewide gross domestic product is forecast to double in size.

The percentage of residents aged 65 and over currently comprises 10.5% of our population. By 2040, that population will be nearly  10% larger  than it is today. However, due to socioeconomic and health disparities, average life expectancies can vary  over 20 years  between census tracts in Harris County.

Climate change worsens health inequities present in our communities by placing additional stress on the social, economic, and environmental conditions where we live, learn, work, and play.  According to the CDC  and the  U.S. Department of Health and Human Services , these conditions known as the Social Determinants of Health are shaped by resources and factors that affect a wide range of health, functioning, and quality of life outcomes. Some of these determinants of health are structural as they are built into the governing process or policies. Examples of structural and social determinants of health include safe and affordable housing; access to education, job opportunities, and income; racism, discrimination, and public safety; availability of healthy foods and physical activity opportunities; local emergency/health services; and air and water quality.

The degree to which people and places are able to cope with the impacts of climate change defines their vulnerability or resilience to a particular climate risk. Recent reports by the  Intergovernmental Panel on Climate Change  and the  U.S. National Climate Assessment  both project disproportionate impacts of climate change on vulnerable populations, which include children, the elderly, the sick, the poor, and some communities of color.

Houston’s efforts to address climate change can also improve the social determinants of health, and vice versa. The  Houston Climate Action Plan  (CAP) and  Resilient Houston  both include actions to lessen the impacts of climate change, by reducing greenhouse gases and through adaptation. For example, actions that increase tree canopy and safe access to parks, schools, and local foods (especially in neighborhoods with traditionally fewer amenities and resources) also increase health equity by reducing pollution, chronic illness, and injury. Houston’s trees reduce air pollution, including  carbon dioxide  and particulates;  reduce urban heat  and  storm water runoff ; and provide food and habitat for wildlife.

Environmental hazards and extreme events have historically disproportionately harmed vulnerable communities. The CAP identifies the need for youth and environmental justice working groups as a path for vulnerable populations to have a voice in implementing climate solutions. The City is working to ensure those residents and the informal knowledge they hold about their lived experiences and community history are uplifted.

Houston has a history of being impacted by many climate and weather extremes. The most recent severe drought in Houston lasted from 2010 to 2015. The drought’s worst impacts were felt in 2011, when the drought combined with one of the worst heat waves on record. From 2015-2019, Houston experienced  six large-scale rain events  that resulted in significant flooding across much of the city.

Houston is a  coastal city  situated along the Gulf of Mexico coastal plain. Among the flattest metropolitan areas in the U.S. with a slope less than one foot per mile, the city's elevation varies from around 30 feet in the eastern portion of the city near Buffalo Bayou to around 80 feet in the west and 150 feet in northwest portion of the city. Due to this low elevation, the Port of Houston--one of the busiest seaports in the world--and Ship Channel are becoming more susceptible to sea level rise and hurricane-induced storm surge which can have significant economic and community impacts. Sea level rise is expected to  increase the frequency and extent of extreme flooding  linked to coastal storms.

Globally, climate is changing  due to human activities  and a rate unprecedented in contemporary times. Since 1900, the average temperature around the world has  increased by about 1.8°F  (1°C) and the global average sea level has  risen by about 7-8 inches . Increased temperature is causing  animals and plants to move into new areas .  Ice contained in glaciers has declined ,  Arctic sea ice has decreased  at an accelerating rate, permafrost is thawing, and extreme heat and rainfall are becoming more frequent.  Extremely cold and extremely hot temperature s are projected to increase. While cold waves are expected to be less intense,  heat waves are expected to be more intense . 

Climate change has affected our  built environment, urban systems, and cities ;  water  quantity, quality, infrastructure, and management;  energy  supply, delivery, and demand; and  agriculture and rural communities . In the United States, the number of weather and climate related disasters causing billions of dollars in damage have increased since 1980 and their total costs have increased, as well. Texas and Houston have felt a substantial portion of those costs. Since 1980, Texas experienced  129 of the 291 billion dollar extreme weather events in the U.S.  recorded in NOAA’s database and incurred  10-15% of expenses  related to all disasters in the database. Texas experienced  56.9% these expenses in the last five years (2016-2020) .

According to the  Climate Impact Assessment , since 1950, Houston has seen increases in temperature, hot days, warm nights, and the length of summer (which begins earlier and ends later). From now through the year 2100, Houston will likely experience increases in temperature, extreme precipitation events, drought, and length of summer and multi-day heat waves. Energy demands for cooling in buildings will likely increase in spring, summer, and fall. Total annual precipitation is not expected to change much because summer precipitation is expected to decrease while fall precipitation is expected to increase.

Drought events are extended dry periods with little or no rain that can have devastating and cascading impacts on our health, economy, and environment by affecting our food, energy, infrastructure, and water resources.

Houston is known for its hot, humid, long summers. As temperatures rise, summers lengthen, and heat waves linger, Houstonians must bear with the extreme heat associated with the changing climate. Extreme heat occurs when the temperature and humidity levels are well above average. Scorching temperatures negatively affect human and animal health, the energy sector, transportation, and overall quality of life.

Extreme temperatures are not new to Texas, but heat is a stressor when there is no relief. There have been several heat waves over the year, most notably in  2011 during an extreme drought . Average temperature throughout the city during the month of August exceeded 100°F, resulting in higher death and  emergency department visits  attributed to the extreme weather. The peak recorded temperature that month was 109°F at IAH on August 27, 2011.

Energy consumption in buildings can be split into two categories, the energy use that must occur to keep the building function or “baseload” and the energy use specific to the type of business that occupies the building and to weather variations or “variable load”. Typical baseload energy needs include security systems, server rooms, refrigeration, and main area lighting. Temperature, humidity, wind, and precipitation affect how much energy the building consumes, particularly the heating and cooling energy demand. Cooling accounts for about 12% electricity consumption in commercial and institutional buildings or about 4% of total U.S. electricity consumption.

The concept of cooling degree days (CDD) is used to estimate the effect of weather on building cooling energy use. The number of CDDs in a given period is defined as the difference between the average temperature and 65 °F (18 °C). For example, if the mean temperature is 80 °F, then CDD = 80 – 65 = 15.

The neutral base temperature of 65 °F is assumed to be adequate for human comfort indoors, and counting the difference between the outdoor temperature and that point of comfort via CDD gives an approximate idea of the amount of energy needed to cool the inside of a building to that base temperature. 

The total CDD for a month, season, or year counts the total number of degrees above 65 °F on all days in that period. For example, a July with 31 more CDDs compared to an earlier year would have had a 1°F increase in temperature on average for the month. A higher total CDD means the period is warmer and more cooling is needed.

Between the 1971-1990 and 2001-2020 periods, Houston saw increases of around  140 CDDs per summer, 90 CDDs in spring, and 110 CDDs in fall . In the next two decades, CDDs are expected to increase in spring, summer, and fall. The greatest changes are projected for summer. Due to warmer temperatures and longer summers, cooling demand is projected to increase by about  170 CDDs in spring, 250 CDDs in summer, and 200 CDDs in fall . The growing trend in CDDs results in higher energy costs and more stress on the power grid. 

As CDDs increase, building energy demands and energy burdens could increase with them, disproportionately impacting low-income residents who already spend higher percentages of their income on energy.

 Extreme rainfall (or precipitation) events  occur when precipitation is in the top 1% of all days with precipitation.

The updated climate predictions in the  Climate Impact Assessment  were conducted with a newer method of scaling global climate models down to a regional level.  The model improves predictions  for rare but impactful events that effect infrastructure, agriculture, and human health.

Results from the Kinder Area Survey show that fewer Harris County residents agree more severe storms are almost certain (down from 81% in 2018 to 59% in 2021). However, 71% of residents believe their government should prohibit construction in flood prone areas and 85% believe that better land use planning to guide development is needed. Additionally, the number of Houstonians who thought people and businesses should be free to build wherever they want dropped from 24% in 2020 to 15% in 2021.

The  Houston Climate Action Plan  and  Resilient Houston  identified gaps in Houston’s capacity, policy, programs, assets, and knowledge that will need to be addressed as Houston makes strides to increase resilience and adapt for climate change. Energy efficiency improvements and clean energy investment will decrease Houston’s energy demand and associated climate impact, but traditional financing for energy efficiency has limits. Additionally, educational attainment helps to determine long-term economic opportunity, but there are wide socioeconomic disparities in this region.

Since 2017, the trauma felt by all Houstonians as a result of Hurricane Harvey exposed gaps across Houston’s infrastructure and programs. Sections of bayou corridors are weak links for flooding. Information access for all residents of Houston, many of whom do not speak English, is a critical gap for safety and emergency preparedness. Message coordination and capabilities are lacking. Gaps in mental and behavioral health services, especially for our children, must be addressed in disaster preparedness, response, and recovery.

In the  Houston Climate Action Plan  and  Resilient Houston , the City of Houston has outlined goals to identify additional gaps in capacity, policy, programs, assets, and knowledge. For example, the City will lead a policy review to identify existing City policies and programs that reinforce historical disparities and limit socio-economic opportunities for some Houstonians, particularly vulnerable populations and historically disinvested neighborhoods. Additionally, the Solid Waste Management Department (SWMD) is conducting a gap analysis of current operations that will end in recommendations for increased landfill diversion as well as environmentally sound and financially stable future actions.

The Houston area has many existing policies, programs, assets, capacities, and actions available to leverage to build climate and resilience solutions. The  Climate Action Plan  emphasizes that existing and emerging hubs, partnerships, and accelerator programs will advance and deliberately build upon our strong research foundation to solve big problems.

Houston is a top destination for clinical health care and medical research. The Texas Medical Center is the world’s largest medical complex and its member institutions are consistently recognized as some of the best hospitals and universities in the nation. The City’s expansive network of health professionals at Houston’s Medical Center, Texas Children’s Hospital, Baylor College of Medicine, Menninger, and numerous preschools, public and private schools, and local colleges and universities will be called upon to increase opportunities for collaboration in health and medical research for climate mitigation and adaptation.

The University of Houston’s  Center for Carbon Management in Energy  aims to identify solutions to lead the lower carbon future for the energy industry. Rice University has launched the  Carbon Hub  in partnership with industry leaders to advance research on efficient, deployable carbon technologies that will enable a zero-emissions future. Rice’s  Energy and Clean Technology Venture Forum , Ion Houston, and Greentown Labs are also leading the development of “clean tech” in Houston. 

The City is bringing together many local community organizations and efforts to achieve its climate and resilience goals. For example, the City of Houston built upon ongoing efforts such as Houston’s Safer Streets Initiative, the Houston Bikeways Program and Houston Bike Plan, the Vulnerable Road Users Ordinance, Walkable Places, CIGNA Sunday Streets, and goals set by the Texas Transportation Commission to reduce the number of deaths on Texas roadways to develop a  Vision Zero Action Plan .

Finally, Houston’s community is its greatest store of knowledge. Houston and Harris County held the  largest community-led urban heat mapping effort  in the nation in August 2020. Data were released in January 2021. A robust community-informed approach to creating equitable policies will mitigate negative impacts, spread benefits, and ensure that policies are flexible enough to adapt to future needs.

While great strides have been made, research, analysis, planning, and innovation efforts in the Houston area could help us make even bigger changes. The  Climate Action Plan  and  Resilient Houston  include research plans such as developing a competitive advantage strategy for energy transition and carbon management, including creating an energy innovation ecosystem; encouraging and increasing scalability of carbon capture, utilization, and storage; and promoting Houston as an innovation hub and research center for new energy technologies. Plans are also aimed at improving Houston’s land, air, and water, such as bringing vacant properties in urban core neighborhoods back into productive use; improving water management; increasing nature-based infrastructure; and conducting research on the source of hot spots of formaldehyde toxic air pollution in Houston. 

The  Climate Action Plan  identifies weatherization as one of the necessary actions to achieve climate goals. Houston lags other major cities in Texas and the Lone Star State has fallen behind other states in implementing weatherization per capita. Research may be needed to quantify the total population needing weatherization in Houston and to prioritize efforts to close the gap between those who need weatherization and those who are receiving it, including ensuring those who qualify are not deferring maintenance that never occurs. The City of Houston does not administer any weatherization programs but can work with program administrators and listen and learn from the community members who need weatherization to improve this process.

Some of Houston’s challenges will require research to be incorporated with neighborhood engagement, strategic policy recommendations, and pilot programs. This change will also benefit the community by increasing connections between the members of Greater Houston’s innovation ecosystem.

The  Houston Climate Action Plan  and  Resilient Houston  have many important short- and long-term goals that will address risks and vulnerabilities throughout the Houston area. Some of these goals include reducing costs and barriers for alternative transportation among vulnerable populations; supporting small business to better withstand disruption; enhancing and expanding systems to rapidly house Houston’s homeless population and provide them with the supportive services that they need to remain in housing; enhancing City infrastructure to further promote accessible and integrated service delivery for all and reducing vulnerabilities for aging and disabled residents during emergencies and disasters; preparing for rising temperatures through neighborhood-based interventions that combat extreme heat and the urban heat island effect; embracing the  One Water  movement; advancing comprehensive construction and maintenance of green stormwater infrastructure; enhancing multilingual communication and engagement opportunities; and leveraging environmental justice mapping and research to inform decision making.

 Resilient Houston ‘s number one goal is to ensure Houstonians have the information, skills, and capacity to prepare for any emergency with tasks such as developing cash and direct assistance programs for vulnerable populations during disaster recovery. Approximately  39% of Houstonians  do not have $400 for an emergency situation, including 44% of Black and 45% of Hispanic  44-45% of Black and Hispanic residents of Harris County . Additionally, 40% of Black residents and 37% of Hispanic residents had a problem paying for their housing in 2020. Approximately a quarter of all Harris County adults aged 19 to 64 cannot afford to see a doctor, and more than 27% do not have health insurance, including 41% of Hispanic residents. Adaptive capacity to the effects of changing climate will be limited for residents experiencing these hardships. Houston’s heat and flooding will continue to be risks for low-income Black and Hispanic residents, as well as disabled, elderly, and pregnant people and children. Climate adaptation and mitigation solutions will need to prioritize vulnerable populations most sensitive to a changing climate. 

While the future is uncertain, we can expect that Houston will only face increasing challenges over the next 30 years. The steps we take today can begin to shape the future for the next generation of Houstonians.