Climate and Weather
Weather and climate aren’t the same. Weather is the condition of the atmosphere in any particular time and place. It consists of temperature, air pressure, humidity, clouds, precipitation, visibility, and wind.
But measuring those elements at a particular location (Belém, for example) over many years and calculating their long-term averages provides a picture of the climate for that location.
So weather information helps you decide if you might need an umbrella this afternoon, while climate data tells you whether you could expect enough rain to grow certain crops.
Climate is more than just averages, though. Hurricanes, heat waves, droughts, floods, and other extreme events are also part of climate—in particular, how often they occur and how intense they are. Even volcanic eruptions can affect climate for a few months or years. All of these aspects of climate can change over time—sometimes slowly, over millennia—and sometimes in months or years.
Scientists have figured out most of what caused major changes in past climates, including drifting continents, changes in Earth’s orbit and tilt, the accumulation of snow and ice, asteroid impacts, and volcanic eruptions. They also know how natural climate variations like El Niño and La Niña affect climate in the short-term. And they know that the relatively recent changes in climate that we are observing are caused by none of these.
So what is causing them? To understand that, we first need to understand one of the most important aspects of climate—something called the Greenhouse Effect. We’ll discuss that next.