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Climate Change

The Greenhouse Effect

Naturally occurring atmospheric gases such as carbon dioxide, methane, nitrous oxide and others trap the Sun's heat keeping the Earth sufficiently warm to sustain life. Without such greenhouse gases (GHGs), the Earth would be inhospitable.However, human activity over the last 250 years - primarily the overuse of fossil fuels such as coal, oil and gas - have increased GHGs in the atmosphere and unnaturally trapped too much heat. As a result, we have begun to experience a warming of our climate which is adversely affecting our weather, oceans, ecosystems and society.

Image of Earth's Greenhouse Effect
The following short videos from the National Aeronautics and Space Administration (NASA) provide visual and graphic depictions of climate change:



Scientific Consensus and Observed Changes

There is widespread scientific consensus that human activities have increased the concentration of GHGs in the atmosphere, and that this increase has affected the Earth's climate system. 

According to the Intergovernmental Panel on Climate Change (IPCC), a scientific body representing 195 countries under the auspices of the United Nations:

Images of three graphs of the IPCC climate study findings on warming climates worldwide.
IPCC, 2013: Summary for Policymakers -
  • Warming of the climate system is unequivocal, and since the 1950's, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.

  • Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. In the Northern Hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1400 years (medium confidence).

  • Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (high confidence).

  • The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901 - 2010, global mean sea level rose by 0.19 meters (7 1/2 inches).

  • The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification. 

  • It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

  • Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse has emissions.

  • View the IPCC Report as downloadable chapters.


Impacts of Climate Change

The impacts from climate change are already apparent, increasingly exposing society to risk.  Climate change impacts virtually all aspects of life, ranging from agricultural crop yields, precipitation levels, ecosystems, human health and the economy.

Image of Earth

According to the United States Environmental Protection Agency, global average temperatures have increased by more than 1.4 degrees Fahrenheit over the last century, and that for every 2°F of warming, we can expect to see:

  • 5—15% reductions in the yields of crops as currently grown

  • 3—10% increases in the amount of rain falling during the heaviest precipitation events, which can increase flooding risks

  • 5—10% decreases in stream flow in some river basins, including the Arkansas and the Rio Grande

  • 200%—400% increases in the area burned by wildfire in parts of the western United States

Scientists also project that the Earth's average temperatures will rise between 2 and 12 degrees Fahrenheit by 2100. (National Research Council)


The Impact of Climate Change on Maryland

Maryland is already witnessing climate change impacts:

  • Maryland’s climate has become wetter and hotter over the last 30 years, resulting in more stormwater runoff and longer heat waves.

  • August and September of 2011 were the wettest the state has seen in 117 years.

  • July of 2010, 2011, and 2012 were the hottest on record across much of the state.

  • Sea levels along the State’s coast have risen approximately one foot over the last 100 years. Data from the Maryland Department of Environment.


The most significant impacts of climate change on Maryland are likely to be those related to sea level rise, increasing temperatures and unstable precipitation patterns.  With Maryland having the fourth longest tidal coastline, sea level rise can have dramatic impacts on the state’s environment and economy.  

Read the state of Maryland Climate Change Reports:


The Montgomery County Climate Action Plan

Montgomery County, Maryland has been a national leader in addressing climate change. From the early adoption of climate protection objectives to the implementation of ground-breaking programs designed to expand the use of clean energy, increase the energy efficiency of buildings, or develop new transportation initiatives, the County has sought effective and innovative solutions to reducing the County’s climate footprint.

The 2009 County Climate Protection Plan (PDF, 3.45MB) represents a major step in the County’s efforts. The Plan contains 58 specific recommendations across a broad spectrum of activities to ensure that Montgomery County remains at the forefront of local governments addressing climate change.

The Climate Protection Plan was created by the Sustainability Working Group (SWG) which consisted of 26 representatives from County government, regional organizations, and the public.

Image of Silver Spring GreenFest
The County Executive, Councilwoman Valerie Ervin, DEP staff and local dignitaries celebrating the launch of Capital BikeShare in the County and the Silver Spring GreenFest.

To help with the development of the Plan, the SWG established committees which focused its deliberations and recommendations on seven distinct areas:

  • Renewable Energy

  • Residential Building Energy Efficiency

  • Commercial/Multi-Family/Public Building Energy Efficiency

  • Transportation

  • Forestry & Agriculture

  • Long-Term Planning (including Land Use Planning)

  • Education & Outreach

View the County law that created the SWG and spawned the Climate Protection Plan. 

Although the SWG has since disbanded, the Climate Protection Plan has proven to be a very useful framework for action.  Almost all of the recommendations have been or are being implemented by County government departments and agencies and community organizations.

Read the 2009 County Climate Protection Plan (PDF, 3.45MB)

View the May 2011 Implementation Status Document (PDF, 104KB)


Commercial and Multi-Family Energy Efficiency Study

The Montgomery County Department of Environmental Protection (DEP) hired an independent consultant to identify and explore specific policies and programs to help the County attain the goal identified in the Climate Protection Plan to reduce energy consumption in the commercial and multi-family building sector by 25% by 2020.

The study includes: 

  • An analysis of the buildings making up the commercial and multi-family sector

  • An evaluation of the potential energy savings associated with the implementation of various policies and programs, and a discussion of the technical and economic issues associated with their implementation

  • The results of a stakeholder survey regarding these potential policies and programs, and specific comments, 

Many of the policies outlined in the study, if implemented could result in a reduction in greenhouse gas emissions, reduce energy costs to County businesses, and assist in improving the long term value and economic viability of our commercial building stock and multi-family communities. However, the study is frank regarding the economic, logistical, and policy challenges that may need resolved before any specific policy can be implemented. 

Moving forward, the County is evaluating the proposed options with community, business and other stakeholders to develop a Commercial and Multi-Family Strategy to make progress towards the County’s aggressive goal. 

If you have questions on the Study or Montgomery County’s Commercial and Multi-Family Programs please contact

Download the Montgomery County Commercial and Multi-family Building Study  (PDF, 2.4MB)



What You Can Do!

As a direct result of the Climate Protection Plan, the Montgomery County Department of Environmental Protection developed the interactive website My Green Montgomery, a one-stop-shop to green living.

Image of My Green Montgomery

My Green Montgomery provides residents with a list of sustainability actions spanning:

  • Energy

  • Water

  • Lawn and Garden

  • Transportation

  • Daily Living

Throughout the year, DEP staff and guest writers from local nonprofits, businesses and the County community post articles and stories about how to “go green” and reduce your impact on the environment.  A selection of articles include, “How I Greened My Church”,  “Homeowners Join Forces to Save Energy” and “The Silver Spring GreenFest”.

If you’re interested in writing a guest blog for My Green Montgomery, email

The website also has a calendar of environmental education events open to the public, an interactive blog, links to resources, community groups and an extensive directory of “green” incentives.

Stay Connected!: Get the latest green news by subscring to the monthly My Green Montgomery e-Newsletter.