Press Releases
09/03/2025
CT’s Latest Climate Report Shows Emissions in 2023 Decreased in the Two Largest Sources of Climate Pollution: Transportation and Buildings
Economy-wide Emissions Increased, But Remain Below Pre-pandemic Levels
(HARTFORD) — The Connecticut Department of Energy and Environmental Protection (“DEEP”) published its latest Greenhouse Gas (“GHG”) Emissions Inventory, a comprehensive documentation of Connecticut’s air pollution that contributes to climate change. DEEP has issued this report since 2003, and also now in accordance with Public Act 25-125, signed into law by Governor Lamont earlier this month.
This year’s inventory shows that in 2023, which is the most recent year for which data is available, emissions decreased from the two largest sources of climate pollution in our state: transportation and buildings. Additionally, after a significant drop in overall emissions in 2020 due to the COVID-19 pandemic, economy-wide emissions continued to increase for a third consecutive year but remained 9.5 percent below pre-pandemic levels in 2019.
Transportation emissions decreased for the first time since 2019 by 2%, despite people, on average, driving more miles per vehicle. The decrease in emissions was most likely due to a larger share of more efficient light-duty vehicles on the road. Residential buildings sector emissions decreased by 5.6% predominantly due to the milder winter. These two sectors remain the state’s top two sources of GHG emissions due to the burning of fossil fuels with transportation at 42% and residential buildings at 19% followed by commercial buildings at 12%.
This year’s inventory report release coincides with EPA’s recent announcement that it plans to repeal the landmark “endangerment finding” that concluded that greenhouse gases are a threat to public health and the environment. Connecticut has long recognized this fact, publishing the state’s first GHG Inventory more than two decades ago to identify the sources of emissions, benchmark the state’s progress towards reducing emissions, and to inform policy decisions.
“The evidence is in: greenhouse emissions in 2023 declined in transportation and buildings, as a result of strong federal and state programs that provide clean air, improve energy affordability, and protect public health” said DEEP Commissioner Katie Dykes. “This summer, Connecticut experienced four heat waves in less than two months, and unhealthy air due to wildfire smoke, and we continue to see stronger storms and damaging flooding fueled by climate change. Addressing these impacts continues to be an urgent challenge. As we celebrate this progress in reducing emissions, we are concerned that recent actions by the EPA to roll back power plant regulations, vehicle fuel economy standards, and even the Endangerment Finding, will remove critical federal tools that contributed to this progress.”
"Clean air is the backbone to human health and keeping economy-wide emission levels below pre-pandemic levels is a success," said DPH Commissioner Manisha Juthani, M.D. "Poor air quality exacerbates existing health problems and creates new ones, affecting both immediate and long term wellbeing. Greenhouse gas emissions significantly impact human health by contributing to climate change, which in turn leads to various health problems including respiratory illnesses, heat-related illnesses, infectious disease outbreaks, food and water insecurity, and mental health issues. Amid the EPA pulling back on these efforts, Connecticut will hold our values to protect and improve the health and safety of our residents."
“While transportation remains the largest source of greenhouse gas emissions in the state, through strategic investments and programs, we’re making cost effective improvements,” said CTDOT Commissioner Garrett Eucalitto. “Whether it’s growing the state’s battery electric bus program, offering more public transportation options, or making infrastructure safer for bicycles and pedestrians, we’re committed to ensuring sustainable and efficient transportation options are available throughout Connecticut.”
While progress has been made since 1990 toward emission reduction goals, there is significant work to be done to meet pollution reduction benchmarks set by the legislature including the new benchmark to reduce emissions by 65% from 2001 levels by 2040 and net-zero by 2050, provided emissions are reduced at least 80% below 2001 levels. During the first wave of the Covid-19 pandemic in 2020, Connecticut met an emission-reduction goal set by the 2008 Global Warming Solutions Act. Reaching the next goal - 45 percent reduction in GHG emissions from 2001 levels by 2030 - requires reducing 8.9 million metric tons of carbon dioxide equivalent (MMTCO2e) from 2023 emissions by 2030. If Connecticut continues to reduce its emissions at its current average pace since emissions peaked in 2004, the state will achieve a 40% reduction in emissions below 2001 levels by 2030. To meet the 45% goal, the state would need to reduce its emissions by an additional 2 MMTCO2e by 2030.
Pursuant to Public Act 25-125, DEEP will release later this year an analysis of what the state’s emissions are expected to be in 2030, 2040, and 2050 based on current state and federal policies. This analysis will serve as a first step in determining additional actions the state can take to further reduce emissions as part of the Comprehensive Climate Action Plan to be completed by July 1, 2026. The Act also directed DEEP to prepare a “triple impact” report by February 1, 2026 with strategies that lower energy costs for families and businesses, increase community resilience to extreme weather events, and reduce greenhouse gas emissions. DEEP is also in the process of developing its next Integrated Resources Plan, which assesses the supply and demand needs of the electric sector over the next ten years and makes recommendations on how to achieve the state’s climate and energy policy goals.
"Connecticut deserves credit for tracking emissions as the state works to meet clear, scientifically driven goals to reduce climate pollution” said Daniel Sosland, president of Acadia Center. “Acadia Center thanks DEEP for making emissions information publicly available, allowing the state and stakeholders to see where progress is being made and better adjust to challenges in the effort to build a clean energy economy. Addressing climate is essential to positioning Connecticut for a stronger economic future, reducing energy costs, and making needed improvements in housing and transportation that will improve the quality of life in its communities.”
“This latest Greenhouse Gas Inventory Report underscores the significant work still needed to achieve our climate goals” said Charles Rothenberger, Director of Government Relations for Save the Sound. “The data shows that although emissions have generally declined since their peak in 2024, they have risen each of the last three years, albeit at a slowing rate. Even if we maintain our overall historic downward trajectory, a business-as-usual approach will still fall short of what is needed to meet our obligations in 2030 and beyond. To succeed, we must accelerate the adoption of zero-emission vehicles and clean heating technology, expand access to renewable energy, and maximize our investments in energy efficiency. These measures will not only allow us to meet our climate goals but also reduce energy costs and ensure cleaner air and healthier outcomes for our residents.”
“The Greenhouse Gas Inventory is not only important to track Connecticut’s contributions to global warming, but is also an indicator of air pollution,” said Dr. Mark Mitchell, a public health and environmental health physician. “The largest source of GHG by far is transportation, which leads to air pollution-related asthma, learning delays, and other health conditions. This pollution is concentrated in urban, low-wealth communities composed of residents who are more exposed, but are less likely to own these polluting vehicles. The good news is that these emissions are now declining, due to increased fuel economy standards that were adopted over the last decade or more. We must continue to move toward cleaner cars, trucks and buses for the sake of our health, as well as for our planet.”
Other high-level takeaways from the GHG Inventory include:
- In 2023, Connecticut’s GHG emissions were 35.0 million metric tons (MMT) of carbon dioxide equivalent (CO2e), up 1.5 percent from 2022. The increase in emissions in 2023 was driven largely by an increase in emissions associated with the generation of electricity for consumption in state resulting from a lower availability of zero-carbon electricity.
- In 2025, the state enacted an Act Concerning the Protection of The Environment and Development of Renewable Energy Sources and Associate Job Sectors, which established a GHG reduction target of 65% below 2001 levels by 2040.
For the complete report, go here: Connecticut Greenhouse Gas Emissions Inventory 1990–2023
To view previous GHG Emissions Inventories, go here: CT Greenhouse Gas Inventory Reports
Learn more about the Comprehensive Climate Action Plan
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Contact
DEEP Communications
DEEP.communications@ct.gov
860-424-3110