Climate Change

What Is It? What Causes It? What Can We Do About It?

By Alejandro Reuss | March/April 2015

This article is from Dollars & Sense: Real World Economics, available at

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This article is from the March/April 2015 issue.

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We expect the weather to change from day to day. One day it’s sunny; the next, rainy. The temperature one summer day might be 80°F; the next day, 95°. We also expect weather to change with the change in seasons. The average temperature in July in the northern hemisphere, for example, is much higher than the average temperature in January.

This primer on climate change was originally a sidebar to Maine Farmers and Climate Change: Reactive or Proactive?, by Stephanie Welcomer, Mark Haggerty, and John Jemison.

Climate change is different. Changes in day-to-day weather conditions, so long as these still vary around the same averages for that particular place at that time of year, year after year, do not indicate climate change. Nor do particular weather conditions in a particular place—like unseasonable cold or unusual snowfall—tell us much about climate change, one way or another. Rather, climate change is the long-run shift in underlying weather patterns (including temperature, precipitation, etc.).

What are the key indications that the climate is actually changing?

Average surface temperatures have been trending up over the last century. This doesn’t mean that, every single year, average temperatures are necessarily higher than the year before, still less that we will never see unusually cold weather. The upward drift in temperatures is confirmed by the fact that we’re setting record highs more often, and record lows less often, now compared to the past.

Also, we can observe receding surface ice, including the polar ice caps and other major ice sheets. The polar ice caps cover more area during the winter than during the summer. However, they do not cover as large an area at any given time of year as they used to. The Greenland ice sheet, too, has exhibited higher-than-normal summer melting in recent years.

What are the causes of climate change?

Greenhouse gases in the atmosphere, such as carbon dioxide, trap energy from the sun, letting it get to the planet’s surface but not letting it just reflect off back into outer space—much as the glass walls and roof of a greenhouse let heat in and trap it inside. Without the greenhouse gases in our atmosphere, the earth would be much colder.

There have certainly been large-scale climate changes over time, before human behavior could possibly have had a meaningful impact on the climate. Over the last couple of centuries, however, human activities—especially the burning of fossil fuels for heat, electricity, and transportation—have dramatically increased the atmospheric concentration of carbon dioxide. What we are concerned about today is anthropogenic (human-caused) climate change.

Plants take carbon dioxide from the atmosphere and release oxygen, trapping the carbon. This is known as carbon sequestration. Over millions of years, the organic material from long-dead plants and animals have been turned into chemicals called hydrocarbons—found in coal, petroleum, and natural gas. When we burn these fuels, we join the carbon with oxygen, and produce carbon dioxide. In other words, in a very short time we are undoing millions of years’ worth of carbon sequestration.

Human emissions of greenhouse gases not only have a direct effect in increasing surface temperatures, but can also set off other processes that accelerate climate change. Rising temperatures, for example, result in higher atmospheric concentrations of water vapor, which can also act as a greenhouse gas. The melting of surface ice, meanwhile, means that the earth reflects less energy back into outer space. These are known as positive feedback loops—not because they are desirable, but because they amplify the climate change that is already under way. Human economic activity, in addition, contributes to climate change not just through greenhouse gas emissions, but also through actions, like deforestation, that reduce carbon sequestration. (Deforestation actually results in both emissions and reduced sequestration.)

Why is climate change cause for concern?

Higher surface temperatures may seem desirable for various reasons—warmer weather can be more pleasant, it can lead to longer growing seasons for agriculture, and so on. However, there are major reasons for concern about climate change.

Even small increases in temperature can disrupt ecosystems and human activities that rely on them. In agriculture, for example, it may make a particular locale inhospitable to the kinds of crops that farmers are accustomed to planting, or result in changing pest populations, requiring a change in methods of pest control.

Rising ocean temperatures and melting of surface ice leads to a rise in sea level, which will lead to flooding of coastal areas. The flatter a coastal area, the more of the land’s surface will flood, for any given rise in sea level. Already, it appears inevitable that some small island nations will be completely submerged within a short span. Countries like Bangladesh, with a long coastline and very flat terrain, are especially vulnerable to rising sea levels. A one-meter rise could flood one-fifth of the country’s territory, according to the Intergovernmental Panel on Climate Change.

Another negative effect could be increased frequency of extreme weather events. While it’s not possible to say that any particular storm is caused by climate change, climate scientists are concerned that climate change will make severe storms more frequent. For example, increased ocean temperatures could mean more energy to feed cyclones, resulting in more Category 5 hurricanes.

What are some possible responses to climate change?

Responses to climate change fall into two broad categories— climate adaptation and climate mitigation. Climate adaptation means changing our behavior to deal with climate change. For example, we might build seawalls and other coastal flood-control systems. These don’t prevent climate change, but can prevent the coastal flooding that would otherwise come with it. Farmers might change the kinds of crops they grow to cope with changes in average temperatures, or might apply different kinds of pesticides to cope with changes in the local pest population.

Climate mitigation means taking action that prevents climate change, whether by reducing greenhouse gas emissions or increasing carbon sequestration. We can reduce emissions in three main ways—by reducing our total production of goods and services, by reducing the amount of energy we use per unit of production (increased energy efficiency), or by reducing the amount of carbon dioxide we emit per unit of energy (reduced carbon intensity). For example, we could increase the energy efficiency of industrial production (as businesses find ways to do when energy prices are high), shift toward less carbon- intensive energy sources for electrical-power generation (for example, away from coal and towards wind and solar energy), reduce our use of petroleum for transportation (shifting toward more fuel-efficient vehicles or alternative modes of transportation), or reduce our energy use in heating and air conditioning our buildings (building better-insulated structures, or retrofitting existing buildings). People can also increase the rate of carbon sequestration, for example, by promoting reforestation.

What kind of future can we anticipate?

What we know now is that some climate change is already happening, and some future changes to our climate are now unavoidable, so we will have to make some adaptations. It is not too late, however, to commit to serious climate mitigation, which may be the only way to prevent even more severe climate change. In fact, it is crucial that we do as much as we can as soon as we can. We should be worried that we’re steering towards a “climate cliff,” unleashing irreversible effects to which we really have no good way to adapt—for example, dramatically rising sea levels, frequent extreme storms, or severe disruptions to agriculture.

Some people scoff at the possibility that we puny human beings can really do much damage to the earth. Whatever we do, the earth will go on. Whether it goes on in a way that is hospitable to the planet’s inhabitants, however, is another matter. Both rich and poor cluster near the world’s coastlines. As sea levels rise and extreme storms become more common, the rich will retreat to higher ground—at some cost, but at little risk of losing everything. The world’s poor lack the resources to move easily. The rich will manage, whatever the disruptions to agriculture, to get plenty to eat. Small farmers in the developing world, in contrast, will bear the brunt of climate disruptions. The rich, of course, consume more than the poor and so benefit the most from activities that give rise to climate change. Meanwhile, they have the greatest capacity to adapt, so they have the least stake in mitigation.

In other words, “business as usual” on climate change embodies the worst aspects of our unequal world.

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