Causes of climate change

Humans are increasingly influencing the climate and the earth's temperature by burning fossil fuels, cutting down forests and farming livestock.

This adds enormous amounts of greenhouse gases to those naturally occurring in the atmosphere, increasing the greenhouse effect and global warming.

Greenhouse gases

The main driver of climate change is the greenhouse effect. Some gases in the Earth's atmosphere act a bit like the glass in a greenhouse, trapping the sun's heat and stopping it from leaking back into space and causing global warming.

Many of these greenhouse gases occur naturally, but human activity is increasing the concentrations of some of them in the atmosphere, in particular:

carbon dioxide (CO₂)
methane
nitrous oxide
fluorinated gases

CO₂ produced by human activities is the largest contributor to global warming. By 2020, its concentration in the atmosphere had risen to 48% above its pre-industrial level (before 1750).

Other greenhouse gases are emitted by human activity in smaller quantities. Methane is a more powerful greenhouse gas than CO₂, but has a shorter atmospheric lifetime. Nitrous oxide, like CO₂, is a long-lived greenhouse gas that accumulates in the atmosphere over decades to centuries.

Natural causes, such as changes in solar radiation or volcanic activity are estimated to have contributed less than plus or minus 0.1°C to total warming between 1890 and 2010.

Causes for rising emissions

Burning coal, oil and gas produces carbon dioxide and nitrous oxide.
Cutting down forests (deforestation). Trees help to regulate the climate by absorbing CO₂ from the atmosphere. When they are cut down, that beneficial effect is lost and the carbon stored in the trees is released into the atmosphere, adding to the greenhouse effect.
Increasing livestock farming. Cows and sheep produce large amounts of methane when they digest their food.
Fertilisers containing nitrogen produce nitrous oxide emissions.
Fluorinated gases are emitted from equipment and products that use these gases. Such emissions have a very strong warming effect, up to 23 000 times greater than CO₂.

Global warming

2011-2020 was the warmest decade recorded, with global average temperature reaching 1.1°C above pre-industrial levels in 2019. Human-induced global warming is presently increasing at a rate of 0.2°C per decade.

An increase of 2°C compared to the temperature in pre-industrial times is associated with serious negative impacts on to the natural environment and human health and wellbeing, including a much higher risk that dangerous and possibly catastrophic changes in the global environment will occur.

For this reason, the international community has recognised the need to keep warming well below 2°C and pursue efforts to limit it to 1.5°C.

气候变化的原因
人类通过燃烧化石燃料、砍伐森林和饲养牲畜，对气候和地球温度的影响越来越大。这增加了大气中自然产生的大量温室气体，增加了温室效应和全球变暖。
温室气体
气候变化的主要驱动因素是温室效应。地球大气中的一些气体的作用有点像温室里的玻璃，捕获太阳的热量，防止它泄漏回太空，导致全球变暖。其中许多温室气体是自然产生的，但人类活动正在增加其中一些气体在大气中的浓度，特别是:
二氧化碳(CO2)
甲烷
一氧化二氮
氟化气体
人类活动产生的二氧化碳是全球变暖的最大贡献者。到2020年，它在大气中的浓度已经上升到比工业化前(1750年前)的水平高出48%。其他温室气体是由人类活动排放的，但排放量较小。甲烷是一种比二氧化碳更强的温室气体，但其大气寿命较短。一氧化二氮和二氧化碳一样，是一种长期存在的温室气体，在大气中积累几十年到几个世纪。据估计，自然原因，如太阳辐射的变化或火山活动，对1890年至2010年的总变暖的贡献不超过正负0.1°C。

排放增加的原因
燃烧煤炭、石油和天然气会产生二氧化碳和一氧化二氮。
砍伐森林。树木通过吸收大气中的二氧化碳来帮助调节气候。当树木被砍伐时，这种有益的作用就丧失了，储存在树木中的碳被释放到大气中，加剧了温室效应。
增加畜牧业。牛和羊在消化食物时产生大量的甲烷。
含氮化肥会产生一氧化二氮的排放。
含氟气体由使用这些气体的设备和产品排放。这种排放具有非常强烈的暖化效应，比二氧化碳的暖化效应高出2.3万倍。
全球变暖
2011-2020年是有记录以来最热的十年，2019年全球平均气温比工业化前水平高出1.1°C。人类引起的全球变暖目前正以每十年0.2°C的速度增加。与前工业化时代相比，气温升高2摄氏度会对自然环境和人类健康和福祉产生严重的负面影响，包括全球环境发生危险和可能发生灾难性变化的风险大大提高。出于这个原因，国际社会已经认识到有必要将升温控制在2摄氏度以下，并努力将升温控制在1.5摄氏度以内。