Climate change is the change in the mean state of the climate over time, i.e., a statistically significant change in one or both of the mean state of the climate and the departure (distance level) together. The larger the value of the outlier, the greater the magnitude of the climate change and the more unstable the climate state. The term refers to changes in the state of climate on various time scales. The range is from the longest billions of years to the shortest interannual variability. It can be divided into geologic climate change, historical climate change, and modern climate change. The scale of climate change in geological period is about 104-108 years, and it is mainly studied indirectly based on fossils of animals and plants and various relics. The scale of climate change in the historical period is about 102-103 years, during which there were human beings, and it is mainly based on historical records, changes in flora and fauna, and analysis of tree annual rings. The scale of climate change in the historical period is about 102 to 103 years, which is mainly based on historical records, changes in flora and fauna, and analysis of tree chronology, etc. During this period, there were alternating changes between warm and cold periods, dry and wet periods, and there were both synchronous and reverse changes in different regions of the world. It is generally believed that from the end of the 19th century to the first half of the 20th century, the climate in the northern hemisphere warmed up over a wide area, especially the Arctic and high latitudes, the temperature rose significantly, while the southern hemisphere did not change much, and the warming phenomenon reached a peak around 1940, after which it began to become cold. The causes of climate change are complex.

The causes of climate change may be natural internal processes, external forcing, or ongoing anthropogenic changes in atmospheric composition and land use. There are both natural and anthropogenic factors. Among the anthropogenic factors, the main ones are due to human activities since the industrial revolution, especially the economic activities of the industrialization process in developed countries. Emissions of greenhouse gases from human activities such as fossil fuel combustion and deforestation, and land use changes have led to a significant increase in atmospheric greenhouse gas concentrations and an enhanced greenhouse effect, thus causing global warming. According to a study by the Oak Ridge Laboratory, the world has emitted more than 1 trillion tons of carbon dioxide since 1750, with developed countries accounting for about 80% of the emissions. What are the impacts of climate change? Climate change has led to frequent catastrophic weather events, accelerated melting of glaciers and snowpack, imbalance in water distribution, and threats to biodiversity. Climate change will also cause sea level rise, and coastal areas will be more severely affected by natural disasters such as floods and storms, and small island states and low-lying coastal areas are even threatened with inundation. Climate change will adversely affect economic and social activities in agriculture, forestry, animal husbandry and fishery, exacerbate the spread of diseases, and threaten social and economic development and people's health. According to the report of the Intergovernmental Panel on Climate Change, if the temperature rises by more than 2.5℃, all regions of the world may be adversely affected, with developing countries suffering particularly severe losses; if the temperature rises by 4℃, irreversible damage may be caused to the global ecosystem, resulting in significant losses to the global economy. According to the National Assessment Report on Climate Change released by China in 2006, the impact of climate change on China is mainly focused on agriculture, water resources, natural ecosystems and coastal zones, which may lead to increased instability in agricultural production, increased flooding in southern regions, increased conflict between water supply and demand in northern regions, degradation of ecosystems such as forests and grasslands, frequent occurrence of biological disasters, sharp decrease in biodiversity, typhoons and storm surges, increased disasters in coastal zones, and impacts on the safety of construction and operation of major projects.

The global consensus among scientists is that more than 90% of climate change is likely to be the responsibility of humans themselves, and that the decisions and choices humans make today will influence the course of climate change. Today, the planet is hotter than it has been in the past 2,000 years. If conditions continue to deteriorate, by the end of this century, the Earth's temperature will climb to a two-million-year high.

For more than 100 years, humans have relied on fossil fuels, such as oil and coal, to provide the energy they need to live and work, and the burning of these fossil fuels emits greenhouse gases, such as carbon dioxide, which are the main cause of the increased greenhouse effect and, consequently, global climate change. About 1/5 of the greenhouse gases are also emitted due to the destruction of forests, which reduces the ability to absorb carbon dioxide. In addition, some special industrial processes and agricultural animal husbandry also emit a small amount of greenhouse gases.

In China, coal dominates the total energy consumption. from 1979 to 2005, the average share of coal resources consumption in the total energy consumption was 72.4%. In terms of relative changes in the consumption of various energy sources, although the share of coal in total energy consumption shows a slow decline, its absolute consumption is rising, with coal consumption accounting for about 67%. Coupled with the fact that China's energy efficiency is not high, such a high reliance on coal for development is not sustainable, and in the face of the growing global warming problem, people have only one choice: they must take immediate action.

About the causes of climate change

Greenhouse principle: Solar radiation is mainly short-wave radiation, while ground radiation and atmospheric radiation are long-wave radiation. The atmosphere has a strong absorption of long-wave radiation and a weak absorption of short-wave radiation.

During the day, when sunlight hits the earth, part of the energy is absorbed by the atmosphere, part is reflected back to the universe, and about 47% or so of the energy is absorbed by the earth's surface.

At night, the Earth's surface emits the energy absorbed during the day to the universe in the form of infrared light, most of which is absorbed by the atmosphere.

As a result, the atmosphere is like a greenhouse covered with glass, which can preserve a certain amount of heat, so that the Earth is not like the moon, where the temperature rises sharply when it is illuminated by the sun and falls sharply when it does not see daylight.

How to recognize the greenhouse effect: Imagine if there were no greenhouse effect, the Earth would be too cold for human habitation. It is estimated that without the atmosphere, the Earth's surface temperature would be minus 18 degrees Celsius. It is the greenhouse effect that keeps the Earth's temperature at 15 degrees Celsius. The moon, as we know it, can reach temperatures of 127 degrees Celsius during the day where the sun shines vertically, while at night the temperature can drop to minus 183 degrees Celsius because there is no atmosphere.

Why is the Earth warming? Quite simply, there is an imbalance between income and expenditure. Like saving money, the Earth's bank gets more income (heat) than it spends (energy radiated out), so naturally the temperature rises.

One of the major causes of the greenhouse effect is greenhouse gas emissions. The greenhouse effect is enhanced by the increase in greenhouse gases, and carbon dioxide is the most abundant greenhouse gas. Today, the surface of the earth emits far more carbon dioxide outward from the combustion of natural gas in long-wave heat spokes than it did in the past. On the other hand, indiscriminate deforestation and the building of large amounts of agricultural land into cities and factories have destroyed vegetation and reduced the conditions for converting carbon dioxide into organic matter. This, combined with the gradual shrinking of surface waters and the greatly reduced precipitation, has reduced the conditions for absorbing dissolved carbon dioxide and disrupted the dynamic balance of carbon dioxide production and conversion, which has increased the carbon dioxide level in the atmosphere year by year. The increase in the amount of carbon dioxide in the air causes a change in the temperature of the Earth.

The understanding of the process, severity and impact of climate change on different regions is still evolving, but scientists have confirmed the following.

1. certain gases, such as carbon dioxide, create a greenhouse effect in the atmosphere, preventing heat from reflecting back into space and keeping the Earth's temperature from rising.

2. Burning fossil fuels (e.g., coal, oil, etc.) releases more carbon dioxide into the atmosphere.

3. Although carbon dioxide is not the strongest greenhouse gas, the level of carbon dioxide produced by human activities has increased dramatically and has become the culprit of the enhanced greenhouse effect.

4. The concentration of carbon dioxide in the atmosphere has reached its highest level in 650,000 years.

5. The 1990s can be considered the hottest decade in history, and 1998 was the hottest year of all.

The following points are also widely agreed upon.

6. It seems inevitable that the global average temperature will rise by 1.3 degrees Celsius compared to the pre-industrial revolution due to the emission of greenhouse gases such as carbon dioxide. Limiting the increase to 2 degrees Celsius is a way to prevent more serious disasters from climate change.

7. If greenhouse gas emissions are not controlled, the rate of climate change will be the fastest in human history.

8. Climate feedback mechanisms are likely to bring about dramatic and irremediable chain reactions, and no one knows the extent to which climate change will lead to the "end of the world".

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