Climate change impacts

A warming atmosphere leaves little unscathed

Polar bear coming out of the water

In 2008, the polar bear became the first animal to be added to the Endangered Species Act (as a threatened species) because of global warming.

Allan Hopkins/Flickr

Because there are so many impacts of climate change, scientists have broadly categorized them into three areas:

  1. Erratic climate and weather extremes
  2. Altered ecosystems and habitats
  3. Risks to human health and society

1.The primary impact: Earth's water systems thrown off balance

Hurricane Katrina

Hurricane Katrina, a massive Category 5 storm, caused widespread destruction in 2005.

Photo credit: NOAA

Emissions of heat-trapping gases from human activity—especially the burning of fossil fuels for energy—cause our atmosphere to heat up.

This atmospheric heating unleashes a torrent of rapid changes to the way water systems typically function on our planet.

For example:

  • The cryosphere—the frozen water on Earth—is melting. A warmer atmosphere causes the planet's snow pack, glaciers and sea and freshwater ice to melt at an accelerated pace. Melting glaciers and polar ice sheets contribute to sea level rise. As the ice melts, it also exposes more dark ocean waters, which absorbs more sunlight than ice, and thus heats the ocean more, triggering a cycle of melting and heating.

  • Weather of all kinds is getting more extreme: The increased evaporation of water is like fuel for storms, exacerbating extreme weather events, such as hurricanes. Rising sea levels make coastal flooding events worse. In more naturally arid areas, droughts and wildfires intensify.

  • The oceans are getting hotter, expanding, and becoming more acidic: The oceans are getting hotter, because they soak up 90% of the extra heat in the atmosphere. This causes the oceans to expand, and this also contributes to higher sea levels. Meanwhile, the increased concentration of carbon dioxide in the ocean triggers a chemistry change that makes the water more acidic. The ocean is almost 40% more acidic than it used to be.

2. This shift in water patterns then alters natural habitats


Many Arctic animals, including seals, depend on seasonal ice to breed and raise young.

Photo credit: Digital Vision

As climatic patterns rapidly shift, habitats on land and in the sea are changing, making them inhospitable for some species, while letting others move in and take over. In some cases, entire ecosystems are at risk of collapsing.

The changes to the natural world are vast, but here are three notable and well-documented examples.

  • Coral and shellfish are suffering: Coral reefs are highly sensitive to small changes in ocean temperatures. The heat stresses the algae that nourish the corals and provide their vibrant colors. The algae then leave, and the corals eventually starve, an event known as bleaching. Also, a more acidic ocean affects the normal calcium balance, meaning creatures with calcified shells, such as shellfish and coral, may not have enough calcium to grow.

  • Forests are more prone to deadly infestations: Milder winters and longer summers allow tree-killing insects to thrive. Meanwhile, trees weakened by prolonged drought have lower defense mechanisms. This cycle of warmer weather, weak trees and thriving insects is likely the culprit behind the massive die-off of 70,000 square miles of Rocky Mountain conifers.

  • Our Arctic creatures need ice, but it's vanishing: As sea ice disappears, ice-dependent mammals like walruses and polar bears struggle to survive. In 2008, the polar bear became the first animal to be added to the Endangered Species Act list of threatened species because of global warming.

3. It also places many added burdens on people and society

Woman with ears of corn

Aissata Abdoul Diop, of Mauritania, shows how ears of corn have dried due to drought.

Photo credit: Pablo Tosco/Oxfam

Human life is thrown out of balance, too. One of the biggest impacts? Where, how and when we grow food, which is vitally connected to our climate's normal patterns.

More extreme weather also means we face increased pressure on our health, infrastructure, and economy.

  • Climate change is a major threat to agriculture: The toll that climate change takes on agriculture is nearly incalcuable, and as a result, our food security is at risk. All over the world, farmers are struggling to keep up with shifting weather and increasingly unpredictable water supplies. Farmers also must contend with unexpected attacks from weeds, diseases and pests, which affect yield.

  • Warmer, polluted air affects our health: A warmer atmosphere increases chemical reactions that form ground-level ozone, also known as smog. Smog is a well-known lung irritant and a major trigger of asthma attacks. Smoke from wildfires further degrade the air. Extreme summer heat will mean more deaths during heat waves, and warmer freshwater makes it easier for pathogens to grow and contaminate drinking water.

  • Infrastructure and transportation are at risk, too: Hot weather, flooding and other extreme weather events damage infrastructure, put heavy burdens on electrical supplies, and disrupt how we travel and commute.

Make your voice heard

If we don't rein in heat-trapping emissions from burning fossil fuels and deforestation now, these impacts will only intensify. You can help by supporting measures to make polluters reduce climate emissions. We'll tell you when your voice is needed. (Read our privacy policy.)

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