Advanced Search
Climate change is the greatest environmental threat confronting the world. While there have been natural shifts in Earth's weather patterns for eons, the changing climate over the past few hundred years has been driven overwhelmingly by human activities. Activities such as burning fossil fuels increase the concentration of greenhouse gases like carbon dioxide in the atmosphere, trapping more heat from the sun and raising global temperatures. Carbon dioxide is the primary greenhouse gas driving global climate change, though methane, hydrofluorocarbons, and other gases also contribute to a warming planet.
The effects of climate change can be seen worldwide in all aspects of life. Climate change is causing vast shifts in ecosystems and weather patterns, including stronger hurricanes, more intense wildfires, longer droughts, and an ice-free Arctic. Climate change is also detrimental to human health, could shrink economies, endangers national security, and is affecting and will continue to affect every part of society.
There is an urgent need to address climate change. Energy efficiency and renewable energy are the fastest, safest, cleanest, and most cost-effective means of reducing our use of fossil fuels and preventing the worst effects of climate change. Nature-based solutions, like ecosystem conservation and climate-smart agricultural practices, help protect biodiversity and natural systems while also storing carbon dioxide. In addition, techniques such as the direct capture of carbon dioxide from the air (direct air capture) and the capture, use, and storage of carbon emitted by industrial facilities will be necessary to reduce the carbon dioxide levels already present in the atmosphere.
Read more on climate change: Fossil Fuels | National Security and Energy Independence
Several gases, such as carbon dioxide and methane, exist naturally in the atmosphere and contribute to the warming of the Earth's surface by trapping heat from the sun—a process known as the greenhouse effect. When the share of such greenhouse gases in the atmosphere is stable, the effect is beneficial, making surface temperatures friendly to life on Earth and reducing temperature swings.
Human activities like burning fossil fuels emit potent greenhouse gases, including carbon dioxide, methane, and nitrous oxide, among others. The concentration of carbon dioxide in the atmosphere in 2021 was 417 parts per million (ppm), which is higher than it has ever been over the last 800,000 years. Before the Industrial Revolution in North America and Europe, which began in about 1760, carbon dioxide levels averaged about 280 ppm. The rate at which carbon dioxide is being added to the atmosphere has been accelerating as well. In the 1960s, the growth rate was about 0.6 ppm per year. During the 2010s, that rate increased to 2.4 ppm per year.
There is broad scientific agreement that human activities, most notably the burning of fossil fuels for energy, have led to the rapid buildup in atmospheric greenhouse gases. Over 97 percent of actively publishing scientists agree, and have written so in numerous peer-reviewed scientific journals.
In a 2021 report providing an update on the physical science of climate change, the Intergovernmental Panel on Climate Change, a global body of the United Nations that provides scientific information about the climate crisis, wrote: “It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.”
A Global Consensus: The United Nations Intergovernmental Panel on Climate Change
The leading international organization for the study of climate change is the Intergovernmental Panel on Climate Change (IPCC), which operates under the umbrella of the United Nations. The IPCC, established in 1988, has 195 member governments, all of which participate in the review of its reports and endorse its findings. IPCC reports are policy-neutral, offering knowledge without prescribing solutions. The IPCC does not conduct its own research; instead, more than 1,000 experts review and assess available science from many thousands of peer-reviewed studies conducted worldwide in many different disciplines. The IPCC publishes a report every five to seven years which collects the latest science on global climate change. In addition, the IPCC also occasionally publishes special reports on key subjects, such as reports on what the impacts of 1.5°C of global warming would be and the future of the ocean and ice expanses in a changing climate.
The first part of the IPCC’s sixth assessment report, covering the physical science of climate change, came out in 2021. The second part, covering the threats climate change presents to natural and socio-economic systems and how these threats can be adapted to, and the third part, covering mitigation options that limit or avoid greenhouse gas emissions, were both released in 2022. All three reports will be condensed into a Synthesis Report, including a Summary for Policymakers, which is scheduled for release in March of 2023.
Using air bubbles trapped in ice cores, scientists are able to measure the level of carbon dioxide in the atmosphere as far back as 800,000 years ago. They observed that carbon dioxide levels started increasing exponentially in the mid-20th century, to levels higher than at any time over the past 800,000 years. The rate at which carbon dioxide is being added to the atmosphere continues to increase. In the 1960s, about 0.6 parts per million (ppm) of carbon dioxide were added to the atmosphere each year; in the 2010s, that rate increased to 2.3 ppm per year.
As the concentration of carbon dioxide in the atmosphere has increased, so have global temperatures. Since 1880, the average global temperature has increased by about 2 degrees Fahrenheit (1.1 degrees Celsius).
An American Perspective: The U.S. Global Change Research Program and the National Climate Assessment
The United States government regularly conducts a wide-ranging analysis to understand the domestic effects of climate change, as mandated by the Global Change Research Act of 1990 (P.L. 101-606). To fulfill this legal requirement, the U.S. Global Change Research Program (USGCRP) was established in 1989 and given the task of producing a National Climate Assessment (NCA) every four years. USGCRP coordinates with the 13 federal agencies that fund climate change research to produce the NCA.
The Fourth National Climate Assessment, released in two parts in 2017 and 2018, breaks down climate trends in 10 regions of the United States: the Northwest, Midwest, Northeast, Southwest, Northern Great Plains, Southern Great Plains, Southeast, U.S. Caribbean, Alaska, and Hawaii and U.S.-affiliated Pacific Islands. The report covers an extensive range of climate issues, such as forecasts of energy supply, effects of sea level rise, and adaptation strategies in U.S. cities. The report also examines how climate change is affecting economic growth, human health, Indigenous livelihoods, and U.S. infrastructure. More than 300 scientists from across the public, private, nonprofit, and academic sectors worked on the report. The Fifth National Climate Assessment is underway and expected to be published in 2023.
Climate change is a global challenge. The effects of rising temperatures, melting ice, rising sea levels, stronger storms, more frequent droughts, more intense wildfires, and other impacts will be felt across the planet. However, not all countries will experience the effects at the same time or with the same intensity.
Climate change is already having catastrophic consequences for people around the world, from deadly heatwaves in Japan to mega-fires in California to powerful typhoons in India to severe droughts in Europe. Disasters such as these will only increase with the continued fossil-fuel burning that drives more carbon dioxide emissions and higher temperatures.
Mass migrations are also already occurring because of climate change. An average of 20 million people are forced to move each year because of climate-driven hazards, a number that is expected to continue to grow.
As atmospheric concentrations of carbon dioxide rise, oceans also absorb more carbon, causing ocean waters to become acidic. Acidic conditions make it more difficult for organisms such as corals and crustaceans to form hard shells or skeletons, ultimately affecting the entire marine food chain—and human consumption of seafood.
Overall, climate change is affecting every aspect of our lives and the lives of every living organism on this planet. It is an existential threat that requires global cooperation to solve.
We can improve the energy efficiency of our buildings, vehicles, and energy generation sector. We can transition to clean renewable energy resources that do not emit new greenhouse gases into the atmosphere. In addition, responsible land management practices that protect forests and soils can help keep carbon out of the atmosphere and conserve ecosystems. Ramping up the deployment of renewable energy and energy efficiency technologies will not only provide environmental benefits—it will also provide jobs and economic growth.
In addition to the transition to clean energy, conserving our ecosystems and implementing nature-based solutions such as wetland preservation, living shoreline installation, and climate-smart agricultural practices can help reduce greenhouse gas emissions and lessen climate change impacts.
However, a certain amount of warming is inevitable based on past and current emissions. Implementing carbon capture techniques like direct air capture will be necessary to address the carbon dioxide that has already been released and prevent the worst effects of climate change. Overall, a quick implementation of all of these solutions will be critical to addressing this planetary crisis.
Last updated in October 2022.
View more entries tagged as Climate Change
Top-Rated Climate Nonprofit – 4-Star Charity