1.6: Keeping an Eye on Climate Change

Earth’s warming temperatures—global warming—and the consequences of that warming for Earth’s weather should concern every one of us. Nearly 100 percent of all climate scientists agree that humans are the cause of global warming. Yes, climate varies naturally. But human activities, especially the burning of fossil fuels and the chopping down of forests (i.e., deforestation), have sent Earth’s climate beyond its natural variations. Well beyond. Because we’re the cause, we have the capacity to be the solution.

As you might expect, the ocean plays an enormous role in regulating the severity of the changes ahead. But before we go much further in our journey, it’s helpful to distinguish what scientists mean when they are talking about weather or climate.

Every day of our lives, we experience the changing conditions of the atmosphere, or what we call weather, the instantaneous state of the atmosphere in a particular location. Weather is happening right here, right now. Weather includes several different variables, such as temperature, humidity, clouds, precipitation, and wind. The ocean influences these variables.

As we grow older, we notice patterns in the weather; seasons change, some years feel hotter or colder, some seem wetter or drier. Seasonal, annual, decadal, and even longer timescale patterns in weather define what scientists call climate, the long-term statistics of weather conditions at a given location or globally. Climate represents the probability of a particular type of weather at a given time and place. For example, in California we normally expect hot, dry summers followed by cool, wet winters. Of course, any given day may be hot or cold in any season. But climate includes more than just the statistical average of weather conditions (e.g., average temperature or amount of precipitation). It also includes the type of weather event, its frequency and duration, and its intensity (Environmental Protection Agency 2021). Heatwaves, cold snaps, extreme floods, and droughts exhibit patterns over time that make up the statistics of climate.

A sports analogy can help us differentiate between weather and climate. A baseball player may get a hit or strike out in any given at bat. How they perform over a series of at bats defines their batting average. Hitters with a high batting average hit the ball more frequently. They may still strike out, but on average, they’re going to hit the ball more times than players with lower batting averages. Climate is like a batting average: it’s the weather we expect on average. Weather, however, like a given at bat, is what we get on any given day. A cold day in summer doesn’t mean winter has come. It’s just the weather for that day.

What worries scientists is that since the mid-1800s, Earth’s global climate has been changing faster than normal. Scientists refer to this as global climate change—changes in the statistics of weather conditions for the entire planet. Now, climate has been changing throughout Earth’s history. During the ice ages, much of North America and Europe was covered in glaciers. At other times, Earth has been so hot that the polar ice caps were completely melted. But the changes that brought these “icehouse” and “hothouse” conditions to Earth happened slowly, over the course of millions of years. The pace of change over the past several decades has no natural counterpart in Earth’s past. We hold the key to our climate future. And it begins with our appreciation and understanding of the Earth system.