The current global warming trend is causing physical and biological changes to occur throughout the entire planet and is impacting regional climates, ecosystems, and the organisms that inhabit them in a number of ways. Animal species can only survive within specific ranges of climatic and environmental factors; if conditions change beyond the tolerance of species, or too rapidly for evolutionary adaptations, then animals may exhibit ecological responses to these changes. The threat of extinction to species who are unable to adapt or have limited habitat is expected to increase with climatic changes, and the extinction of some species have already been directly linked to climate change. Changes are animal’s phenology, like migration, breeding, and spring appearance has occurred throughout the world and linked to seasonal variability. Changes in the spatial distribution of animals, particularly poleward and elevational shifts, is occurring as suitable habitat disappears or extends beyond its current range.

Arctic and marine ecosystems are undergoing physical environmental changes that are affecting the species that inhabit them. Temperature change and melting sea ice in the Arctic is adversely affecting species of the region, and sea level rise. Increased sea temperature and higher pH are among the issues changing the planets marine ecosystems. The spread of pests and disease are occurring as a result of milder temperatures. All of these changes threaten the planets ecological biodiversity and changes projected for the environment will increasingly affect all life on Earth.

Greenhouse gas emissions have increased from year to year. Emissions can rise and fall due to changes in the economy, the price of fuel, and other factors.  In 2016, U.S. greenhouse gas emissions increased compared to 2015 levels. This increase was due to a number of factors, including cold winter conditions resulting in an increase in fuel demand, especially in residential and commercial sectors; an increase in transportation emissions resulting from an increase in vehicle miles traveled; and an increase in industrial production across multiple sectors that also resulted in increases in industrial sector emissions.

The primary sources of greenhouse gas emissions in the United States are:

Electricity
Electricity production generates the largest share of greenhouse gas emissions. Approximately 67 percent of our electricity comes from burning fossil fuels, mostly coal and natural gas.

Transportation
Greenhouse gas emissions from transportation primarily come from burning fossil fuel for our cars, trucks, ships, trains, and planes. Over 90 percent of the fuel used for transportation is petroleum based, which includes gasoline and diesel.

Agriculture
Greenhouse gas emissions from agriculture come from livestock such as cows, agricultural soils, and rice production.

Industry
Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy, as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials.