Is climate change real?

Climate change is real — I'll gather the current scientific evidence to show you why.

Yes, climate change is real. This is the conclusion of the overwhelming majority of climate scientists and every major scientific organization that studies the climate.

What scientists mean by "climate change"

Earth's climate has naturally changed throughout its history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods.

However:

> While Earth’s climate has changed throughout its history, the current warming is happening at a rate not seen in the past 10,000 years.

According to the Intergovernmental Panel on Climate Change (IPCC), "Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact."

NASA summarizes the current scientific position as:

> There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.

The U.S. Geological Survey (USGS) states similarly:

> The scientific community is certain that the Earth's climate is changing because of the trends that we see in the instrumented climate record and the changes that have been observed in physical and biological systems.

> The evidence of a warming trend over the past century is unequivocal.

Scientific consensus

> Yes, the vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.

Most of the leading science organizations around the world have issued public statements expressing this, including international and U.S. science academies, the United Nations Intergovernmental Panel on Climate Change, and a whole host of reputable scientific bodies around the world.

Multiple independent studies using diverse methodologies have quantified the consensus, finding between 90% and 100% agreement on human-caused global warming with multiple studies converging on 97% agreement.

Key evidence of a rapidly warming planet

Scientists use information taken from natural sources (such as ice cores, rocks, and tree rings) and from modern equipment (like satellites and instruments) that all show the signs of a changing climate.

Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.

Major lines of evidence include:

1. Global temperature rising: The planet's average surface temperature has risen about 2 degrees Fahrenheit (1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest.

2. Rate of change unprecedented: Current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age.

3. Ocean warming: The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of 0.67 degrees Fahrenheit (0.33 degrees Celsius) since 1969. Earth stores 90% of the extra energy in the ocean.

4. Ice sheets and glaciers shrinking: The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year. Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa.

5. Sea level rising: Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year.

6. Arctic sea ice declining: Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.

7. Other observed changes: Scientific information from thousands of temperature and precipitation recording stations around the world points to a warming trend. Many types of instrumental records point to a climate warming trend, including streamflow records showing an earlier peak in spring runoff; borehole temperature records in Alaskan permafrost as well as water temperature records on land and sea. Physical and biological changes that confirm climate warming include the rate of retreat in glaciers around the world, the intensification of rainfall events, changes in the timing of the leafing out of plants and the arrival of spring migrant birds, and shifting of the range of some species.

In short, the instrumented climate record, satellite observations, paleoclimate data from ice cores and other natural archives, and observed physical and biological impacts all point to the same conclusion: the planet is warming, and the current warming is dominated by human emissions of greenhouse gases such as carbon dioxide.