Scientific consensus on climate change

There is scientific agreement that the Earth has been consistently warming since the start of the Industrial Revolution. This warming is happening very fast compared to past times. It is mostly because of a big increase in air carbon dioxide (CO₂) from things people do. Human actions like burning fossil fuels, making cement, and cutting down forests are the main reasons for this warming. Other gases in the air, like methane and nitrous oxide, also help make the Earth warmer.

Almost all climate scientists who are studying this agree that people are causing climate change. Looking at many science papers together also shows this agreement. The proof that the Earth is warming because of humans has been seen by science groups in all the big industrial countries. In science writing, there is very strong agreement that Earth’s surface has gotten hotter in recent decades, and this is because people release greenhouse gases. No big science group from any country or around the world disagrees with this.

Existence of a scientific consensus

Scientists have studied opinions about climate change since the 1970s. Since the 1990s, most scientists agree that the Earth is warming up because of human activities. They share their ideas through careful studies. Groups like governments and science organizations put together reports to show what most scientists think.

Some important reports come from groups like the Intergovernmental Panel on Climate Change (IPCC), started by the United Nations in 1988. In 2013, a study looked at many science papers and found that most of them agreed that the Earth is warming up because of humans. Other studies since then have found even more agreement among scientists.

Consensus points

Scientists agree on several key points about climate change and what we can do about it (climate action):

• Human activities, especially releasing gases into the air, have caused the Earth to warm up on land, in the oceans, and in the air we breathe. No natural events can explain this warming.
• The amount of carbon dioxide in the air is now higher than it has been in millions of years. Other gases like methane and nitrous oxide are also at their highest levels in hundreds of thousands of years. These increases happened much faster than natural changes would allow.
• The 2010s were about 1.1 °C warmer than the late 1800s, making them the warmest decade on record. The Earth has been warming faster in the last 50 years than at any time in the past 2,000 years or more.
• Since 1950, there has been more precipitation, but the way rain falls has changed. Heavy downpours that cause sudden floods are happening more often.
• Global sea levels have risen by about 20–25 cm since 1900, with most of that rise happening since 1980. This rapid rise is very likely because of human activity.
• As the ocean warms, it expands, causing half of the sea level rise. The other half comes from melting ice sheets and glaciers.
• While extreme weather like storms, droughts, and heat waves has always happened, climate change is making these events more severe, more frequent, or more likely to happen together everywhere on Earth.
• The risks from extreme weather will keep growing unless we quickly cut down on the gases that cause warming.
• If the Earth continues to warm, the effects will become worse.
• How much more we release these gases will decide how much more the Earth will warm in the future.

Statements by major scientific organizations about climate change

Main article: List of statements by major scientific organizations about climate change

Many big groups that study science have talked about climate change. Most of these groups agree with a group called the IPCC. They think that humans are making the Earth warmer. Only a very small number of groups disagree or stay neutral. For example, a website from the leader of California lists almost 200 science groups that think people are causing climate change.

Surveys of scientists' views on climate change

See also: History of climate change science

1970s

In 1978, experts were asked about future climate changes and their effects on farming. Most thought the Earth would warm up between 1970 and 2000 because of gases people put in the air. A few thought volcanic activity might cool the planet instead. Since then, the Earth has warmed up by about half a degree Celsius.

1980s

In 1989, 21 climate experts were asked about climate change. Seventeen of them strongly believed that big changes in the climate were happening.

1990s

In 1990, 331 researchers answered questions about climate change. Almost all agreed the Earth was warming and that this would cause problems like rising sea levels. They also agreed that cutting down forests and reducing carbon dioxide in the air were good ideas. Only a tiny fraction thought the Earth might cool down in the next 100 years. There was less agreement on how much warmer it would get.

In 1991, 118 scientists were asked if they agreed that the Earth’s temperature was rising. Most agreed, while a smaller group disagreed.

In 1996, researchers asked 1000 climate scientists about their views. Most agreed that warming was happening and would continue. They were less sure about how accurate computer models were, but they still thought it was important to act soon.

2000–2004

In 2003, a survey was done again with similar questions. More scientists now agreed that warming was happening and caused by humans. In 2004, a scientist looked at 928 research papers and found that almost all agreed humans were causing climate change. None disagreed.

2005–2009

In 2007, 489 scientists were asked about climate change. Almost all agreed the Earth had warmed up in the past 100 years, and most thought human activity was helping to warm the planet. Many thought the effects would be dangerous over the next 50 to 100 years.

In 2008, another survey found that most scientists were very sure climate change was happening and caused by humans. They also thought the reports about climate change were accurate.

In 2009, over 3,000 Earth scientists were asked about climate change. Most agreed the Earth was warming and that humans were a big part of the reason. Some groups, like economic geologists and meteorologists, were less sure, but overall, most agreed.

2010–2014

A study in 2010 looked at scientists who published a lot of research on climate. Almost all of them agreed humans were causing climate change. In 2011, another survey of scientists found that almost all agreed the Earth was warming, and most thought humans were causing it. When asked about the future, most thought the effects would be serious.

In 2012, a scientist looked at over 13,000 research papers and found that almost all agreed humans were causing climate change. In 2013, another study of over 11,000 papers found the same thing — almost all agreed.

In 2014, a survey of climate scientists found that the more expert they were, the more they agreed humans were causing climate change.

2015–2019

A study in 2016 looked at the small group of research papers that disagreed with the main view on climate change. They found many mistakes in these papers.

In 2016, another survey asked scientists how sure they were that climate change was happening and caused by humans. Most were very sure. They also thought the risks of climate change had grown since 1996.

In 2017, a scientist looked at many research papers from 1991 to 2015 and found almost all agreed humans were causing climate change. By 2019, this agreement had reached 100%.

2020s

Studies from 2019 to 2021 showed that between 98.7% and 100% of scientists agreed humans were causing climate change.

In 2024, a survey found most scientists thought the Earth would warm up at least 2.5°C by 2100.

In 2021, a survey of Earth scientists found that between 91% and 100% agreed humans were causing climate change, depending on their expertise. Among climate scientists, 98.7% agreed.

Also in 2021, researchers looked at thousands of climate-related studies and found that almost all agreed humans were causing climate change. Only a tiny fraction disagreed.