Climate change is the long term warming of Earth's average temperature, mainly caused by human activities releasing greenhouse gases, leading to widespread and serious impacts on our planet and our lives.

What Causes the Earth to Warm?

Key idea: Human activities release extra greenhouse gases, which act like a thicker blanket around Earth, trapping more heat.

When we burn fossil fuels, cut down forests, and do certain farming or industrial activities, we release gases into the air. These are called greenhouse gases. Think of Earth as having a natural blanket of these gases. This blanket is good because it keeps our planet warm enough to live on. However, human activities are making this blanket much thicker. These extra gases absorb some of the heat that Earth naturally sends back into space after being warmed by the sun. This trapped heat then warms the air closer to the ground.

For example, the amount of carbon dioxide in our air is now about 50 percent higher than it was before the Industrial Revolution. This level has not been seen for millions of years. Carbon dioxide is the main gas causing global warming.

What Are the Effects of Climate Change?

Key idea: Climate change leads to more extreme weather, melting ice, rising sea levels, and serious threats to nature and human well being.

The warming of our planet is already causing many noticeable changes. We are seeing more frequent and intense heat waves and wildfires. In colder regions, like the Arctic, the warming is happening even faster, causing frozen ground called permafrost to thaw, and glaciers and sea ice to melt. Higher temperatures also lead to more powerful storms, longer periods of drought, and other extreme weather events.

These rapid changes are forcing many animals and plants to move to new areas or face extinction. Even if we manage to slow down future warming, some effects will continue for hundreds of years. These include oceans getting warmer, becoming more acidic, and sea levels continuing to rise. Climate change also threatens people directly with more floods, extreme heat, less food and water, more diseases, and economic losses. It can even lead to people having to move from their homes and cause conflicts.

“Even if we manage to slow down future warming, some effects will continue for hundreds of years.”

How Do We Know the Earth is Warming?

Key idea: Long term temperature records and other scientific observations clearly show a steady and significant warming trend.

Scientists use special tools and methods to understand how much the Earth has warmed. They look at things like tree rings and ice cores to understand past climates. Since about 1850, we have had thermometers to track temperatures globally. The Earth's average surface temperature has been increasing by about 0.2 degrees Celsius every ten years.

For example, the decade from 2014 to 2023 was about 1.19 degrees Celsius warmer than the period before the Industrial Revolution (1850 to 1900). It is important to look at long term averages because some years can be hotter or colder due to natural variations, but the overall trend is clearly upward. This warming is also confirmed by other signs, such as the upper atmosphere cooling because heat is trapped closer to Earth's surface, and glaciers shrinking.

Regional Differences and Future Predictions

Key idea: Different regions warm at different rates, with land and the Arctic warming faster, and future warming depends heavily on our emissions.

Not all parts of the world warm at the same speed. Land areas, for instance, are warming almost twice as fast as the global average. This is because oceans can store a lot of heat and lose more heat through evaporation. The Northern Hemisphere, especially the Arctic, is warming much faster than the Southern Hemisphere. This is partly because there is more land in the North, and also because melting snow and ice mean less sunlight is reflected, and more heat is absorbed.

Scientists predict that there is a high chance the world's average temperature will go above 1.5 degrees Celsius in the next few years. If we continue with high emissions, global warming could reach 3.3 to 5.7 degrees Celsius by the year 2100. To have a good chance of keeping warming below 2 degrees Celsius, we need to limit our total future carbon dioxide emissions to about 900 billion tons, which is roughly 16 years of current emissions.

How Can We Address Climate Change?

Key idea: Addressing climate change requires drastically reducing greenhouse gas emissions and actively removing carbon dioxide from the atmosphere, mainly by switching to clean energy and protecting natural ecosystems.

To tackle climate change, we need to do two main things: reduce the amount of greenhouse gases we release into the air, and increase how much carbon dioxide we remove from the atmosphere. To keep global warming below 2 degrees Celsius, we need to reach 'net zero' greenhouse gas emissions by 2070. This means we need to make huge changes in how we get our energy, how we use land, how our cities are built, and how we transport ourselves and goods.

A big part of this is switching from fossil fuels to clean energy sources like wind, solar, hydropower, and nuclear power. We also need to use less energy overall. In farming and forestry, we can prevent deforestation and restore natural ecosystems to help absorb more carbon. There are also technologies like carbon capture and storage that can trap carbon dioxide from industrial processes, but these are currently expensive and only play a small role.

Adapting to a Changing Climate

Key idea: Adaptation means adjusting to the unavoidable impacts of climate change, but it cannot prevent all harm, especially for vulnerable communities.

Even with efforts to reduce emissions, some climate change impacts are already happening and will continue. So, we also need to adapt to these changes. Adaptation means adjusting to the current or expected effects of climate change. This could involve building flood defenses, developing crops that can handle droughts, or creating early warning systems for extreme weather.

However, adaptation alone cannot prevent all the serious and irreversible impacts. Poorer communities, who have contributed the least to the problem, often have the hardest time adapting because they lack resources. It is a matter of fairness and justice that those most responsible for climate change should help those most affected.

“Poorer communities, who have contributed the least to the problem, often have the hardest time adapting because they lack resources.”

Global Efforts and Agreements

Key idea: International agreements like the Paris Agreement aim to limit global warming through collective action and support for developing nations.

Countries around the world have made agreements to work together on climate change. The Paris Agreement, signed in 2015, is a major one. Its main goal is to keep global warming "well below" 2 degrees Celsius, and ideally under 1.5 degrees Celsius. Unlike older agreements, the Paris Agreement does not set strict emission targets for each country. Instead, countries set their own goals, called Nationally Determined Contributions, and are expected to make them more ambitious every five years.

These international efforts also include financial support for developing countries to help them reduce emissions and adapt to climate change. The challenge is huge, but there is widespread support for action, and many countries are working towards a future with much less carbon pollution.