We can define weather expectations in a region as climate. This expectation is based on knowledge accumulated over many years. It includes not only average temperature, precipitation, cloudiness, and humidity, but also how these values change daily and seasonally. Furthermore, extreme weather values also shape our expectations. In short, climate is a concept that includes the average, variability, and extremes of weather conditions.
Weather can change from one day to the next, but we assume that the climate does not change. This assumption is based on the belief that climate does not change significantly over short time periods in terms of Earth's history, similar to a human lifespan. Historically, the Earth's climate has changed over hundreds of thousands or even millions of years, often due to geological or astronomical factors. Changes in the Sun have also temporarily affected the Earth’s climate. These changes and their causes have long been studied and understood scientifically.
Today’s climate changes differ from past changes in two significant ways. First, current changes are happening at an extremely rapid pace. Only an event like a meteor strike at the end of the age of dinosaurs has caused changes similar in effect. Other natural changes occurred over much longer periods. The second difference is that humans are knowingly causing these changes.
Coal, oil, and natural gas are formed from the remains of living organisms that lived millions of years ago. These organisms absorbed carbon dioxide from the atmosphere and stored carbon in their bodies. After remaining underground for millions of years, this carbon turned into what we now call fossil fuels: coal, oil, and natural gas. Humanity has burned these fossil fuels to generate energy since ancient times. However, since the Industrial Revolution, fossil fuel consumption has increased dramatically. Burning fossil fuels for energy has released carbon, stored underground for millions of years, back into the atmosphere as carbon dioxide.
About 30% of the sunlight reaching Earth is reflected back by the surface and atmosphere. The rest is absorbed by the Earth, warming it. The Earth then emits the same amount of energy back into space as infrared radiation. The balance between the absorbed and emitted energy helps keep the Earth's average temperature stable. Throughout human history, the proportion of gases in the atmosphere has remained stable, and thus, the energy emitted by Earth has been consistently released into space.
However, since the Industrial Revolution, we have burned more fossil fuels, increasing the amount of carbon dioxide in the atmosphere. Gases like carbon dioxide trap the infrared energy emitted by Earth, preventing it from escaping into space. This causes the atmosphere to warm, similar to a greenhouse. Therefore, gases like carbon dioxide, methane, and nitrous oxide are called greenhouse gases. The more of these gases in the atmosphere, the less infrared energy can escape. This is our current situation, and it is causing heat to accumulate in the atmosphere, leading to climate change.
The climate change we are experiencing over the past 150 years is caused by human activity. Major consequences include rising average temperatures, changes in precipitation patterns, increased duration and intensity of droughts, melting glaciers, rising sea levels, more intense and widespread wildfires, and the expansion of infectious diseases. These effects intensify each year, and they will continue to worsen as long as we emit greenhouse gases into the atmosphere.
Carbon dioxide is the most significant greenhouse gas. Its primary sources are the burning of coal, oil, and natural gas. The second major source is land use changes for agriculture. Forests are burned, and the soil is plowed, releasing the stored carbon back into the atmosphere.
Methane is the second most important greenhouse gas. It is released into the atmosphere mainly due to three reasons: industrial livestock production, which emits large amounts of methane; rice cultivation; and leaks during the extraction and transportation of fossil fuels.
Nitrous oxide is released through the use of synthetic fertilizers in agriculture and from combustion in motor vehicles. However, its impact is much smaller compared to carbon dioxide and methane.
To reduce global warming, we must either eliminate or drastically reduce emissions from all sources of these greenhouse gases. This can only be achieved through significant changes in various sectors, especially the energy sector. It is not enough to make minor lifestyle adjustments; we must adopt a sustainable way of living through substantial transformations.
The necessity of such major changes has been discussed in international meetings since the early 1990s. One of the major steps was the signing of the United Nations Framework Convention on Climate Change in 1992. This agreement recognized greenhouse gases as the cause of climate change and emphasized that governments must act to reduce emissions. However, the Kyoto Protocol, based on this agreement, was ineffective as it only required developed countries to reduce emissions. During this period, the scale of required changes became apparent, and governments were hesitant to act. The Paris Agreement, adopted between 2020–2030 to combat climate change, aimed to limit global warming to below 1.5°C. However, current national pledges are insufficient to meet this target, and even if all promises are fulfilled, global temperatures are projected to rise by 3°C.
The realization that governmental measures are not enough to prevent the worsening of the climate crisis has led to significant discontent, especially among young people. Today, young people are leading the climate movement with demands for immediate action to stop the climate crisis.