There are several atmospheric substances that warm the earth by trapping heat; collectively we call them greenhouse gases. They include water vapor, ozone, nitrous oxide, methane, chlorofluorocarbons, and carbon dioxide (CO₂). Without them the earth would freeze, but in abundance they can raise temperatures to dangerous levels, and that is what is currently happening. We can say this unequivocally because climate scientists are unanimous in their view that the earth is heating up; it’s happening more quickly than predicted, and it’s due to human activities. Chief among these activities is the burning of fossil fuels (especially oil and coal) because they release CO₂ when burned, and CO₂ is the most significant contributor to global warming. Indeed, we currently release 35 billion tons of CO₂ into the atmosphere every year.
In 2012, scientists at the National Oceanic and Atmospheric Administration (NOAA) reported for the first time that CO₂ levels had reached 400 parts per million (ppm) in several northern locations. This figure vastly exceeds the natural range for the last 800,000 years of 180 to 300 ppm (Smol, 2012). It is highly significant because for several years climatologists have warned that if we are to keep average worldwide temperatures from increasing more than 2.5 degrees Fahrenheit, the level of CO₂ must be kept at 350 ppm. In turn, keeping the increase below 2.5 degrees is important because many researchers consider that to be the maximum we can sustain without disastrous consequences for the environment and for thousands of species.
Currently, about 70 percent of Americans believe the climate is changing and perhaps as many as 40 percent think this change is due to human activities. But this leaves around 50 to 60 percent (including many politicians and talk-show hosts) who believe that the warming is part of a “normal” trend that has little if anything to do with human activities. At best, this is wishful thinking. But reversing the warming trend would be monumentally expensive and it would require individual sacrifice as well as huge changes in business and industrial practices. Partly because of the sacrifices and expense, the topic of global warming is now as controversial in the United States as is evolution (Reardon, 2011). In fact, it is so controversial that in many school districts throughout the country, science teachers are strongly encouraged not to mention it.* No one disputes that there have been dramatic climatic fluctuations throughout earth’s history that had nothing to do with human activity. Furthermore, many of these fluctuations were sudden and had devastating consequences. But even if the current warming were part of a natural cycle, scientists are convinced that humanproduced greenhouse gases could tip the balance toward a catastrophic global climate change. One source of this concern is the study of ice core data, which show that there is significantly more carbon dioxide in the earth’s atmosphere than at any time in the last 800,000 years. In view of this fact, consider this prediction from an international group of experts: “The mean [average] global temperature by 2070 (or possibly a few decades earlier) will be higher than it has been since the human species evolved” (Barnosky et al., 2012, p. 54).
In 2007, scientists became alarmed at a sudden unexpected increase in the loss of Arctic sea ice. Unlike icebergs and glaciers that form on land, sea ice is frozen ocean water. The importance of sea ice to global climate systems can’t be overemphasized because it reflects back into space about 80 percent of the sunlight (which contains heat) that hits it. But seawater absorbs approximately 90 percent of the sunlight that hits it. Therefore as more ice melts, less sunlight is reflected and more heat is retained, resulting in yet more warming and more melting. Because of this, the polar regions are the most sensitive areas on earth to warming, and the loss of sea ice can accelerate climate change.
Since 1979, scientists have been tracking Arctic sea ice maximum and sea ice minimum data collected from satellites. In the first decade of this century, there was a sudden and alarming decline in the extent of sea ice during the summer months. Indeed, the 6 years between 2007 through 2012 (inclusive) saw the greatest declines in Arctic sea ice since the collection of satellite data began. The average minimum area covered by ice between 1979 and 2000 was 2.6 million square miles, but there was a significant change in 2005 when that figure was reduced to 2 million square miles. Just 2 years later, in 2007, the minimum was further reduced to less than 1.6 million square miles. Then, on September 16, the day that melting ceased in 2012, the extent of sea ice was 1.32 million square miles, 49 percent lower than the 1979‒2000 average. (Fig. 17-3) This difference of 1.28 million square miles represents an area nearly twice the size of the state of Alaska (National Snow and Ice Data Center, 2012).
Scientists are now greatly concerned that the polar regions may have reached a “tipping point,” a point beyond which the warming process cannot be reversed. In fact, the increase in warming is occurring faster than computer models were predicting just a few years ago. Recent estimates held that the Arctic could be ice-free for part of the summer by perhaps as soon as 2030, but some scientists now fear this could happen much sooner. It goes without saying that without sea ice in the summer, polar bears and several other species that depend on it may well become extinct in the foreseeable future.
However, there are more than a few who see financial opportunities in the melting sea ice. The absence of sea ice will drastically reduce the time it takes for ships to travel between Asia and Europe. Furthermore, it will make oil drilling possible and, in fact, Russia, Canada, and the United States already have oil exploration projects in progress. Climate change is the result of the interactions of thousands of factors, and the consequences of these interactions aren’t possible to predict with complete accuracy. But the overwhelming consensus among climate scientists points directly to “human-driven global change” (Barnosky et al., 2012), especially due to the burning of fossil fuels. They also agree that, as a consequence of such climate change, we are already experiencing severe fluctuations in weather patterns along with alterations in precipitation levels, and that these will dramatically accelerate in the next few decades. For example, the extreme drought in the United States in the summer of 2012 (the worst in 50 years) forced many farmers to sell their farms and livestock and has caused dramatic increases in food prices. Ultimately this drought will cost at least a few billion dollars.
In late October of 2012, Hurricane Sandy caused billions of dollars worth of damage along the northeast coast of the United States. Streets in lower Manhattan and several subway tunnels were flooded, millions of households were without power, and thousands of homes were damaged or destroyed in New Jersey, New York, and several other states (Fig. 17-4). Moreover, more than 200 people were killed. While scientists cannot state that any particular storm or severe weather pattern was specifically caused by global warming, they do say that weather will be increasingly unpredictable and that we can expect more extreme and destructive events as temperatures continue to rise.
The destructive results of changing temperatures and precipitation patterns are incalculable. They include loss of agricultural lands due to desertification in some regions and flooding in others, rising sea levels inundating coastal areas throughout the world, increased human hunger, extinction of numerous plant and animal species, and altered patterns of infectious disease. Regarding the latter, health officials are particularly concerned about the spread of mosquito-borne diseases such as malaria, dengue fever, and yellow fever as warmer temperatures increase the geographical range of mosquitoes. Another consequence of human caused global climate change is increasing acidification of the oceans due to absorption of greater amounts of CO₂. The global dangers to ecosystems from ocean acidification are potentially as great as global warming, so much so, in fact, that some marine biologists have termed it “the other CO₂ problem” (Doney et al., 2009). Since the beginning of industrialization in the mid1700s, ocean acidity has increased by 30 percent. If current CO₂ emission rates continue, it could increase a further 150 percent by the end of this century, reaching levels not seen in the oceans for more than 20 million years (Turley et al., 2007).
Tropical coral reefs are particularly vulnerable to acidification. Coral reefs constitute the most diverse marine ecosystems on earth including an estimated one million species, which, in turn, represents up to 25 percent of all ocean-dwelling species. In addition to a tragic loss of biodiversity, there are direct economic effects of the destruction of coral reefs because more than 100 million people depend on them for food (Harrould-Kolieb and Savitz, 2009). As bad as this sounds, the longer-term effects of ocean acidification could be far more catastrophic, affecting tens of thousands of other species. Unless major action is taken soon to reduce CO₂ emissions, ocean ecosystems will probably be seriously affected by 2050 (Gruber et al., 2012); these changes could well be irreversible, or at best they will take generations to rebound. If you think this won’t impact you and all of humanity, just consider that today 20 to 25 percent of the animal protein consumed by humans comes from marine sources (Guinotte and Fabry, 2009) (see Fig. 17-5).
There has been international recognition of the enormity of the problems associated with global climate change, and unprecedented international cooperation has begun. All this is happening because the governments of most nations understand the gravity of the impending crisis. But even though these governments recognize the problem, there is powerful opposition from industry to changes in existing policies. In December 2009, the United Nations sponsored the International Convention on Climate Change in Copenhagen, Denmark; it was attended by representatives from nearly 200 countries. Leading up to this meeting, worldwide expectations ran high that earlier agreements (reached in 1997 at a prior international convention in Kyoto, Japan) would be expanded and strengthened with broader and more rigorous, binding agreements to cut carbon emissions.
The world looked especially to the United States for leadership and, even more, for signs of real commitment. Yet nothing substantive occurred in Copenhagen. Most world leaders indicated that they were fully prepared to commit to major cuts in carbon emissions. But widespread lack of trust in American willingness to make real political commitments (that is, effective legislation passed by Congress) as well as weak support from China led to no formal and certainly no binding agreements. Instead, only a broad statement of goals was made, with no mechanisms to ensure that even these would be met.
Another major international meeting, the United Nations Conference on Sustainable Development, again attended by representatives from almost 200 countries, was held in June 2012 in Rio de Janeiro, Brazil. This ambitious conference, also called the Earth Summit, was widely anticipated as another major opportunity to advance serious global action on climate change and related issues. However, no major initiatives were approved and most knowledgeable observers considered the conference a failure.
Widespread disappointment has resulted from this repeated lack of progress. In fact, it now appears that there is less global consensus and less political leadership, especially by those countries that are the biggest carbon emitters, than there was two decades ago. Where we go from here is not clear, but one thing is certain: The climate will continue to change. It will likely be at least 3 or 4 years before another truly global effort is attempted. What will come of that? And will any decisions actually be implemented in time?