Скачать или смотреть Video 3: Common Misconceptions about Climate Change

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VIDEO SUMMARY
Changes in the Earth’s climate are normal, but the changes we are experiencing now are unprecedented and pose many risks to people and the planet. Even though climate change cannot “cause” an extreme weather event, it is still possible for climate change to influence the likelihood and/or severity of individual extreme events. In very extreme cases, it is sometimes possible to say that a specific event could not have happened without climate change. Ozone depletion and climate change are linked in several ways, but ozone depletion is not a major cause of climate change.


COMPLETE VIDEO CONTENT

If we look back far enough in the history of the Earth, we can see that climate change is a normal part of Earth's natural variability. There is also evidence that rapid, large-scale climate changes have occurred previously in the Earth’s history. For example, researchers believe that 90–120 million years ago the Earth was much warmer than it is now. Likewise, geological and biologic evidence preserved in sediments, rocks, tree rings, corals, and ice sheets reveal that, over the last 2 million years, our Earth’s climate has been dominated by patterns of ice ages and glacial retreats lasting thousands of years. During the peak of the most recent glacial cycle, about 21,000 years ago, massive terrestrial ice sheets extended over large parts of North America and Europe and global temperature was about 13 °C (or 9 °F) cooler than today. Even since the end of the last ice age over 10,000 years ago, the planet has undergone many changes in climate with warming during medieval times and cooling during the “Little Ice Age”.

However, this does NOT mean that the changes in climate we are experiencing now are natural. Rather, the changes in our climate that we are experiencing now and will continue to experience for the next hundred years or more are “anthropogenic,” meaning they are human-caused. Specifically, human activities like burning of fossil fuels, cement production, electricity transmission, production and application of nitrogen fertilizers, tilling of soils and agricultural lands, deforestation, and many other activities produce carbon dioxide, methane, nitrous oxide, and other greenhouse gases. These greenhouse gases act like a blanket around the world, thereby insulating our planet and causing it to warm.

Today’s climate change is also more rapid than any changes in climate we have seen in millions of years. Specifically, it is projected that the likely rate of change over the next century will be at least 10 times quicker than any climate shift in the past 65 million years.

Attributing Extreme Events to Climate Change
However, even though climate change cannot “cause” an extreme weather event, it is still possible for climate change to influence the likelihood and/or severity of individual extreme events. In very extreme cases, it is sometimes possible to say that a specific event could not have happened without climate change.
So, for example, when a severe drought occurs, we likely cannot say that the drought is the direct result of climate change. However, depending on the nature of the drought, we may be able to say that the drought was more likely or more severe due to climate change. And, of course, making those types of determinations would be an outcome from a robust scientific exploration, not simply a guess.

Ozone, Ozone Hole, and Climate Change
When many ozone depleting molecules are present, the ozone layer becomes so thin that we say an ozone “hole” has formed. The most well-known ozone hole forms every spring over Antarctica; however, ozone holes are possible at other latitudes as well.
When a hole forms in the ozone, more ultraviolet radiation from the sun reaches the surface of the Earth. This can be dangerous, as ultraviolet radiation can damage crops and cause cancer in humans.
Ozone depletion and climate change are linked in several ways, but ozone depletion is not a major cause of climate change. Specifically, ozone can contribute to the warming of the Earth by trapping heat. Likewise, ozone depletion can contribute to modest cooling of the Earth. Additionally, many of the same gases that are causing ozone depletion are also contributing to climate change. Fully understanding the relationship between ozone and climate change is highly complex. What is most important to remember is that ozone depletion and climate change are linked in several ways, but ozone depletion is not a major cause of climate change.

Kristin Hayman
Graduate Certificate in Climate Science, Program on Climate Change, University of Washington
May 2022