The Difference Between Weather and Climate
By Marvin Maddox
Let’s take a moment to discuss weather and climate, two terms often used interchangeably though they are very different things.
When we talk about weather, we’re usually referring to the short-term changes in the atmosphere, like when we discuss whether we’ll need a coat or umbrella tomorrow. When we talk about climate, we are talking about longer terms, generally much less specific, and average conditions.
A RECENT EXAMPLE
One example of how weather and climate are misunderstood is the topic of global warming. The current warming of the Earth doesn’t mean that every single day in our neighborhood is going to be warmer or that we’ll never experience a cold day. Case in point: the recent “polar vortex.” During the winter it gets very cold at the North Pole, as should be expected when the sun doesn’t shine there for many months. In the upper air over an area near the North Pole, a band of strong winds (a jet stream) develops and usually helps to keep the cold air trapped. However, as the Earth has warmed, this band encircling the North Pole seems to be weakening. This is apparently what has happened during early February. This enabled the very cold air to bulge southward, even reaching into the northern parts of the United States. Now things are returning to normal. The cold air is retreating, and hopefully the polar jet will be able to keep it contained. Is this going to become a routine event? I don’t know; hopefully research meteorologists will be able to provide more answers. We are entering a new phase in the history of our planet, but it is an example of climate affecting weather.
During the recent polar vortex event, the record-breaking cold over northern parts of the U.S. was not the story elsewhere. Australia was experiencing a major heat wave and temperatures over most of the world were near or even slightly above normal. The last four years have been the four warmest years in world records.
CAUSES OF CHANGE
What causes climate changes? That’s a little complicated and involves a bit of astronomy. The Earth goes around the sun, but so do seven other planets. The sun pulls on the Earth, but so do these other planets. This causes the Earth’s orbit around the sun to be wobbly so that the Earth currently goes through climate change cycles approximately every 100,000 years. The result is a sequence of ice ages and warm periods. The last ice age began to end 18, 000 years ago (glaciers had extended as far south as central Illinois), and most of the glaciers melted by 12,000 years ago. Since then, the Earth’s climate has been fairly stable with only a degree or two of fluctuation (which was, however, still enough to be noticeable and to which we refer to as a “Medieval Warm Period” followed by a colder period after about 1350). Humans have multiplied, built large cities and spread all over the Earth.
Being in an ice age cycle isn’t necessarily a good thing; however, there are some factors that could cause us to end the ice age cycles. This presents a different set of problems.
Let’s first consider greenhouse gases. Like so many things, they are good in the right amounts, as they create a “greenhouse effect,” without which the Earth’s temperatures would remain well below freezing and make the planet uninhabitable for us. Too many greenhouse gases, though, have the same effect on the opposite end of the spectrum.
How? Consider one of the most important greenhouse gases: water vapor. Let’s think about the sky being either cloudy or clear at sunset and remaining the same all night. On a cloudy night, the air has a lot of water vapor that traps the radiation from the Earth and stops the temperature from falling very much. On a clear night, much of the radiation escapes and the temperature goes down. Carbon dioxide, a greenhouse gas, works the same way. If you add more carbon dioxide to the air, it traps more of the Earth’s radiation and keeps the Earth warmer. Again, greenhouses gases in the right amounts serve a purpose in creating the balance we need to be able to live on our planet; too much or too little of a good thing, and we’re in trouble.
During the last 800,000 years (according to data from ice core samples in Antarctica) the amount of carbon dioxide in the atmosphere had remained below 300 parts per million (ppm). In recent years, it has increased about 3-4ppm per year and now stands at 407ppm. This, along with some increases in methane and other greenhouse gases, is causing the increase in the Earth’s temperature. Of course there are other contributing factors, but it’s clear that greenhouse gases are by far the most important.
Is there anything that works the opposite to greenhouse gases? Yes! There are substances that can deflect the sun’s radiation from reaching the Earth. Sulphur dioxide is an important one. During the 1960s, industries burned a lot of coal with a high sulphur content; some of you reading this might remember the acid rain result. The Clean Air Act of 1970 gradually resulted in a reduction of sulphur dioxide sent into the atmosphere.
Volcanic eruptions are another source of pollutants in the upper atmosphere. We don’t have many eruptions now, although in 1991 Mount Pinatubo in the Philippines erupted and caused the temperature over the Northern Hemisphere to be about one degree cooler for a year. During the 1920s, there were enough eruptions worldwide that the average temperature in the United States was slightly lower than in previous years.
So why don’t we stop global warming by injecting sulphur dioxide (or a similar substance) into the upper atmosphere? Most scientists are concerned about the “Law of Unintended Consequences.” Sometimes we start with a good idea, but we end up with tragic, unintended results.
OUR CHOICE
We are left with a decision: either we slow or stop the increase of greenhouse gases, or we end up with the impact of a warmer Earth, like it was millions of years ago when the Earth had higher levels of greenhouse gases and the average temperature was much higher. Warming the oceans raises the sea level. Melting all the ice in Antarctica and Greenland would raise sea levels more than 200 feet.
Our present Earth may not be perfect, but we have adapted to it during the past 12,000 years.
With climate change come other changes that may have catastrophic results to those who call the planet home. Some areas will become wetter; North Carolina seems to be in this category. Many other areas will become drier, resulting in drought conditions and making agriculture impossible. Current “beachfront” towns and cities will be submerged, and areas known now for their heat may become unbearable. Where will current inhabitants go? How will we adapt to the loss of agricultural production? Already we are seeing “climate refugees” pouring into countries, forced to abandon homelands that can no longer support ways of life that have existed for generations.
As Christians, we are told to “love our neighbors.” As we make our choice in the coming years, how we will love them and help them adapt to the new realities a changing climate will bring is a question all of us will have to answer.
Marvin Maddox is a retired Air Force Reserve weather officer and National Weather Service supervisory meteorologist.
