As the Intergovernmental Panel on Climate Change — the world’s authoritative body on climate science — declares, warming of the climate system is unequivocal. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. 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?

Light from the sun passes through our atmosphere and reaches Earth’s surface, where it is absorbed. The Earth’s surface then radiates that heat energy back toward space. 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 plant decomposition and volcanic eruptions, but also 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 about 40 percent 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.

Sunlight hits Earth, which radiates heat back to space unless it’s trapped by greenhouse gases. (NASA)

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 you?

According to the Intergovernmental Panel on Climate Change, significant and disruptive effects of a warming planet are already here. In particular, you are likely to see:

  • More extreme weather: Climate change will drive flooding, dangerous storm surges and wildfires in many parts of the world. Extreme weather events could seriously damage critical infrastructure such as roads, electrical grids, communication systems, and water and sewage systems.
  • Rising sea levels: Coastal communities, with half of the world’s population, are projected to suffer erosion, increased flooding and, in the long term, submergence.
  • Increased water scarcity and decreased food security: Climate change will affect the availability of fresh water around the world, with serious consequences for rural and urban residents. Already, farmers are seeing changes that affect crop yields, and will need climate-smart strategies to adapt.

The IPCC concludes that these effects will increase with greater average rise in global temperatures. By significantly limiting heat-trapping greenhouse gas emissions now, we can still avoid the worst-case scenarios of global warming.

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.)