Climate Change
Climate change is one of the most controversial topics in Earth Science. While its controversy owes more to politics than science, there is a deficiency in understanding the concepts behind this topic. As with all my classes, I approach this topic from the perspective of what the science says about it and not from my personal feelings (though, they closely mirror what science says). I present climate change in the context of anthropogenic climate change (or global warming). I am not here to change your beliefs, but merely present the scientific perspective as it currently stands.
Climate change is potentially one of the greatest threats to our planet of our generation. The premise is that as we increase the output and concentration of greenhouse gases (notably carbon dioxide) in the atmosphere, the temperature will warm due to the greenhouse effect (see below). The increased temperatures and increased CO2 concentrations will lead to massive global changes including, but not limited to: sea level rise; stronger storms on land and sea; loss of glaciers and ice caps; increasing disease outbreaks; ocean acidification; and overall loss of habitat for many organisms around the globe. This page will serve to explain how many of these consequences can come to pass simply by increasing CO2 concentrations. Also, this page will address some of the myths associated with climate change that are meant to cast doubt on the science behind global warming.
Climate change is potentially one of the greatest threats to our planet of our generation. The premise is that as we increase the output and concentration of greenhouse gases (notably carbon dioxide) in the atmosphere, the temperature will warm due to the greenhouse effect (see below). The increased temperatures and increased CO2 concentrations will lead to massive global changes including, but not limited to: sea level rise; stronger storms on land and sea; loss of glaciers and ice caps; increasing disease outbreaks; ocean acidification; and overall loss of habitat for many organisms around the globe. This page will serve to explain how many of these consequences can come to pass simply by increasing CO2 concentrations. Also, this page will address some of the myths associated with climate change that are meant to cast doubt on the science behind global warming.
Greenhouse Effect
The main culprit behind the current warming trend is the greenhouse effect. The greenhouse effect is often depicted as an enemy to life when, in fact, it is responsible for life to exist on Earth. Without the greenhouse effect, the average global temperature would be -18 degrees C or -4 degrees F. As it is, the average global temperature is about 15 degrees C or 59 degrees F.
The greenhouse effect is caused by so-called greenhouse gases. These gases include carbon dioxide, methane, water vapor, nitrogen oxides, and sulfur hexafluoride. The main gases we typically focus on are the first three named. Water vapor doesn't figure much in the global warming discussion because it condenses out of the atmosphere and falls back to the surface as precipitation. Most have heard of carbon dioxide as a greenhouse gas, but methane is about 25 times more potent. Yet, it is the amount of carbon dioxide in the atmosphere that gives us cause for concern.
In 1896, Svante Arrhenius demonstrated that increasing carbon dioxide will lead to an increase in atmospheric temperature. The planet Venus provided more evidence to this hypothesis. With its thick atmosphere made up of almost 97% carbon dioxide, the temperatures on the surface are the highest in the solar system. What little sunlight makes it through the blanket of clouds never leaves and keeps the surface hot enough to melt metal. We call the situation on Venus a runaway greenhouse effect because increasing carbon dioxide falls into a positive feedback loop. With more CO2, temperatures go up. With higher temperatures, water cannot store the CO2 and actually releases it. The oceans get more acidic, which dissolves the calcium carbonate in shells and corals, leading to yet more CO2. CO2 continues to increase and temperatures follow suit. Water evaporates faster and faster as temperatures climb. Eventually, there is no water left on the surface and thus nowhere to store the CO2. We have compelling evidence to suggest that this is what Venus experienced. But why? Venus didn't have fossil fuels or people to burn them. Venus is closer to the Sun, so it receives more solar radiation. Venus never (to our knowledge) developed life, which, on Earth, the photosynthetic versions of take in CO2 and release oxygen. The initial levels of CO2 may have started relatively high and just soared on from there. In any case, Venus stands as a testament to the warming power of carbon dioxide.
The main culprit behind the current warming trend is the greenhouse effect. The greenhouse effect is often depicted as an enemy to life when, in fact, it is responsible for life to exist on Earth. Without the greenhouse effect, the average global temperature would be -18 degrees C or -4 degrees F. As it is, the average global temperature is about 15 degrees C or 59 degrees F.
The greenhouse effect is caused by so-called greenhouse gases. These gases include carbon dioxide, methane, water vapor, nitrogen oxides, and sulfur hexafluoride. The main gases we typically focus on are the first three named. Water vapor doesn't figure much in the global warming discussion because it condenses out of the atmosphere and falls back to the surface as precipitation. Most have heard of carbon dioxide as a greenhouse gas, but methane is about 25 times more potent. Yet, it is the amount of carbon dioxide in the atmosphere that gives us cause for concern.
In 1896, Svante Arrhenius demonstrated that increasing carbon dioxide will lead to an increase in atmospheric temperature. The planet Venus provided more evidence to this hypothesis. With its thick atmosphere made up of almost 97% carbon dioxide, the temperatures on the surface are the highest in the solar system. What little sunlight makes it through the blanket of clouds never leaves and keeps the surface hot enough to melt metal. We call the situation on Venus a runaway greenhouse effect because increasing carbon dioxide falls into a positive feedback loop. With more CO2, temperatures go up. With higher temperatures, water cannot store the CO2 and actually releases it. The oceans get more acidic, which dissolves the calcium carbonate in shells and corals, leading to yet more CO2. CO2 continues to increase and temperatures follow suit. Water evaporates faster and faster as temperatures climb. Eventually, there is no water left on the surface and thus nowhere to store the CO2. We have compelling evidence to suggest that this is what Venus experienced. But why? Venus didn't have fossil fuels or people to burn them. Venus is closer to the Sun, so it receives more solar radiation. Venus never (to our knowledge) developed life, which, on Earth, the photosynthetic versions of take in CO2 and release oxygen. The initial levels of CO2 may have started relatively high and just soared on from there. In any case, Venus stands as a testament to the warming power of carbon dioxide.
This graph shows the concentration of CO2 in the atmosphere over a 400,000 year timeframe. You will notice that prior to about 1975, the concentration barely approached 300 ppm (parts per million) just once. Since that time, we have moved above 400 ppm.
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This graph illustrates temperature fluctuations in the Northern Hemisphere over the last 1000 years. Generally speaking, the temperature fluctuates dramatically from season to season, year to year. Yes, the temperature goes up and it goes down, but the overall trend in the last 50 years has been an exponential increase.
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This graph shows the relative amounts of three of the greenhouse gases in the atmosphere. All three have risen drastically within the last 50 years.
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Myths
With any scientific theory/law/concept/hypothesis, there are always those both within the scientific community and without who disagree with it for any number of reasons. However, this theory is one of the most volatile behind only evolution. Please understand that just because scientists may disagree or debate does not mean that they find the theory controversial. They disagree because that is the nature of science. Scientists are supposed to challenge "established" concepts because we don't know all the information and perhaps never will. We work with an open mind for new, valid information that can change theories and hypotheses. That's how science progresses. But, with regard to climate change, 97% of the thousands of published papers by climate scientists over the last 50 years come to the conclusion that humans are causing global warming. That is a scientific consensus, not a democracy.
The climate does indeed change over time. It will continue to change. This is a favorite argument for deniers. But there was a time when the Earth was completely covered in ice (during the Cryogenian Period about 640 million years ago). If that were to happen again, we would be quite concerned about the ice and cold. There was also a time when the planet experienced its highest sea levels, no ice, and warm temperatures globally. That was called the Cretaceous Period and dinosaurs ruled the planet. Yes, the climate changes, but the current rate of warming isn't natural. That should cause great concern.
With any scientific theory/law/concept/hypothesis, there are always those both within the scientific community and without who disagree with it for any number of reasons. However, this theory is one of the most volatile behind only evolution. Please understand that just because scientists may disagree or debate does not mean that they find the theory controversial. They disagree because that is the nature of science. Scientists are supposed to challenge "established" concepts because we don't know all the information and perhaps never will. We work with an open mind for new, valid information that can change theories and hypotheses. That's how science progresses. But, with regard to climate change, 97% of the thousands of published papers by climate scientists over the last 50 years come to the conclusion that humans are causing global warming. That is a scientific consensus, not a democracy.
The climate does indeed change over time. It will continue to change. This is a favorite argument for deniers. But there was a time when the Earth was completely covered in ice (during the Cryogenian Period about 640 million years ago). If that were to happen again, we would be quite concerned about the ice and cold. There was also a time when the planet experienced its highest sea levels, no ice, and warm temperatures globally. That was called the Cretaceous Period and dinosaurs ruled the planet. Yes, the climate changes, but the current rate of warming isn't natural. That should cause great concern.
Links
The following websites provide information about climate change and the myths about it.
The following websites provide information about climate change and the myths about it.