即使你已经知道气候变化事关重大，重温一下以下几点常识也不无益处。

为什么气候会发生变化？

阳光穿过大气层照到地球后，会产生热量并辐射回大气层。大气层中的某些气体能罩住这些热量并使较低的大气层以及地球表面变暖。

二氧化碳就是这些气体中的一种。自然事件如人类呼吸和火山爆发以及人类活动如砍伐森林和燃烧化石燃料，都会使二氧化碳的浓度增加。据美国国家航空航天局（NASA）统计，人类活动在过去200年间使大气层中二氧化碳的浓度增加了三分之一。

而这造成了一个问题，因为大气层中的二氧化碳的含量越高，大气层罩住的使地球变暖的热辐射就越多。这就是所谓的温室效应。

天气和气候：二者有所不同

因为天气每天都在变化，可能很难感觉到长期的气候变化情况。有些日子比较炎热，而有些日子比较凉快。但不要把天气与气候混为一谈。

当人们说到天气的时候，指的是大气层每天及每小时发生的变化。一个地区因地理位置和季节的不同，其温度、湿度和降雨量也在不断地增加或减少。

而当人们说到气候的时候，指的是某一地区每年的大气层的变化——甚至更常指几十年间或几百年间的变化。气候描述的是长期态势，而这些态势表明，地球正在变暖。

气候变化对非洲意味着什么？

虽然整个世界都受到气候变化的影响，但非洲受到的危害首当其冲。例如，南非在过去40年中已变得越来越热。那里的气温自1960年以来每年平均提高了0.13摄氏度。根据政府间气候变化专门委员会（Intergovernmental Panel on Climate Change）提供的数据，如果这种趋势在整个非洲大陆持续下去，将会出现以下情况：

• 干旱和水灾将更加频繁、更加严重。

• 水资源短缺会加剧，到2020年将有多达2.5亿人口无法获得所需用水。

• 到2100年，非洲部分地区的农作物收成将减少，减幅最高可达90％。

展望解决方案

虽然气候变化的形势很严峻，但我们也有重大的机会做好准备，并尽量减少其影响。气候合作伙伴（Climate Partners）提供了一些社区、企业和个人减少污染的方法实例。 （您也可以在推特Twitter上关注气候合作伙伴。）

Simple facts of climate change

Climate scientists are in nearly unanimous agreement that the Earth’s atmosphere is getting warmer. Over the next 100 years, this warming will affect the way people around the world live.

Even if you know climate change matters, you might benefit from a brush-up on the basics.

Why is the climate changing?

The light from the sun that passes through our atmosphere and reaches Earth is radiated back toward space as heat. Certain gases in the atmosphere trap that outgoing heat and warm the lower atmosphere and the Earth’s surface.

One of these gases is carbon dioxide, and its levels are raised by natural events such as breathing and volcanic eruptions, but also by by human activities such as deforestation and burning fossil fuels. According to NASA, the U.S. space agency, humans have increased the atmospheric carbon dioxide concentration by a third during the last 200 years.

This is a problem because the more carbon dioxide there is in the atmosphere, the more radiated heat the atmosphere traps, making the Earth warmer. This is called the greenhouse effect.

Weather and climate: They’re not the same.

The change in climate over many years can be hard to perceive because of the way our weather changes from day to day. Some days are hotter, and some cooler. But don’t confuse weather with climate.

When people talk about the weather, they refer to day-to-day, hour-to-hour fluctuations in the atmosphere. The temperature, humidity and rainfall increase and decrease continuously depending on location and season.

When people talk about climate, they are talking about how the atmosphere behaves year-to-year or — more commonly — during decades or centuries in a particular place. Climate describes long-term patterns, and these patterns show that Earth is getting warmer.

What does climate change mean for Africa?

Although climate change will affect the whole world, Africa is especially vulnerable. South Africa, for instance, has been getting hotter during the last four decades. Average yearly temperatures there have increased by 0.13 degrees Celsius each year since 1960. According to the Intergovernmental Panel on Climate Change, if these trends throughout the continent continue:

• Drought and flood events will be more frequent and more intense.

• Water scarcity will increase, leaving as many as 250 million people without the water they need by 2020.

• Revenues from crops will drop by as much as 90 percent in parts of the continent by 2100.

Looking toward solutions

Although the facts of climate change are daunting, there are significant opportunities to prepare for and minimize its effects. Climate Partners offers examples of ways some communities, businesses and individuals are reducing pollution. (You can also follow Climate Partners on Twitter.)