Authors: Al Gore
Other scientists have determined that higher levels of CO
2
also stimulate insect populations. Evan DeLucia, a plant biologist working with a team of entomologists at the University of Illinois, tested the impact of higher carbon dioxide levels on soybeans and found that
aphids and Japanese beetles flocked to the soybeans grown in higher CO
2
environments, ate more of the plants, lived longer, and produced more eggs. “
That means crop losses may go up in the future,” DeLucia said.
Other scientists on DeLucia’s team found that higher carbon dioxide levels caused soybeans to deactivate genes that are crucial to the production of chemicals that help to defend them against insects by blocking enzymes in the stomachs of beetles that digest soybean plants, and by
deactivating other genes used by soybeans to lure the natural enemies of the beetles. As a result, according to team member Clare Casteel, the soybeans grown in higher levels of CO
2
“
appear to be helpless against herbivores.”
Higher temperatures are having the same effect in boosting pest populations in most areas of the world. One of the leaders of an Asian international agricultural research group, Pramod K. Agrawal, said, “Warmer conditions and longer dry seasons linked to climate change could prove to be the perfect catalyst for outbreaks of pests and diseases. They are already
formidable enemies affecting food crops.” A team of Indian scientists noted that, because insects are cold-blooded, “Temperature is probably the single most important environmental factor influencing insect behavior, distribution, development, survival, and reproduction.… It has been estimated that with a 2 degree C temperature increase, insects might experience one to
five additional lifecycles per season.”
Scientists at the International Center for Tropical Agriculture, for example, found that the cassava crop in Southeast Asia—worth an estimated $1.5 billion each year—is seriously threatened by
pests and plant diseases that expand with warmer temperatures. According to cassava entomologist Tony Bellotti, “The cassava pest situation in Asia is pretty serious as it is. But according to our studies, rising temperatures could make things a whole lot worse.” Bellotti adds, “One outbreak of an invasive species is bad enough, but our results show that climate change could trigger multiple, combined outbreaks across
Southeast Asia, Southern China and the cassava-growing areas of Southern India.”
Microbes that cause human diseases—and the species that carry them—are also expanding their range. In the highly populated temperate
zones of the world, the prevailing climate conditions in which civilization developed were unfavorable to the survival of many disease-causing organisms. But now that warmer climate bands are moving poleward, some of these pathogens are moving with them.
According to a study in
Science
by Princeton University researcher Andrew Dobson and others, global warming is causing the spread of bacteria, viruses, and fungi that cause human diseases into areas that were formerly hostile to them. “Climate change is disrupting natural ecosystems in a way that is making life better for infectious diseases,” said Dobson. “The accumulation of evidence has us extremely worried.” Another coauthor of the study, Richard S. Ostfeld, said, “We’re alarmed because in reviewing the research on a variety of different organisms, we are seeing strikingly similar patterns of
increases in disease spread or incidence with climate warming.”
Although the prevalence of international travel has increased dramatically and some disease-carrying insects have been unwittingly transported from the mid-latitudes to other regions, the shifting climatic conditions are contributing to the
spread of diseases like dengue fever, West Nile virus, and others. The Union of Concerned Scientists wrote that, “Climate change affects the occurrence and spread of disease by impacting the population size and range of
hosts and pathogens, the length of the transmission season, and the timing and intensity of outbreaks.”
They also noted, “Extreme weather events such as heavy rainfall or droughts often trigger disease outbreaks, especially in poorer regions where treatment and prevention measures may be inadequate. Mosquitoes in particular are highly sensitive to temperature.” Improvements in public health systems are crucial to control the spread of these migrating diseases, but many lower-income countries are pressed to find the resources needed for hiring and training more doctors, nurses, and epidemiologists. They also warned that in many of the areas to which these pathogens and their hosts spread with warmer temperatures, “The affected populations will have little or no immunity, so that
epidemics could be characterized by high levels of sickness and death.”
In the summer of 2012, the United States experienced the
worst outbreak of West Nile virus since it first arrived on the Eastern Shore of Maryland in 1999 and spread rapidly to all fifty states in only four years, during a period of unusually warm temperatures. Dallas, Texas, was the first to declare a public health emergency and began
aerial spraying of
the city for the first time since 1966. As concern peaked,
public safety officials issued an appeal for people to stop calling 911 when they were bitten by mosquitoes.
The disease eventually spread by the end of 2012 to forty-eight of the fifty states, killing at least 234 people.
The late Paul Epstein, a professor at Harvard Medical School and a close friend, wrote in 2001 about the relationship between West Nile virus and the climate crisis. More recently, he said, “We have good evidence that the conditions that amplify the lifecycle of the disease are mild winters coupled with prolonged droughts and heat waves—the
long-term extreme weather phenomena associated with climate change.”
According to Christie Wilcox with
Scientific American
:
They
have been predicting the effects of climate change on West Nile for over a decade. If they’re right, the US is only headed for worse epidemics.… Studies have found that mosquitos pick up the virus more readily in higher temperatures. Higher temperatures also increase the likelihood of transmission, so the hotter it is outside, the more likely a mosquito that bites an infected bird will carry the virus and the more likely it will pass it along to an unwitting human host. In the United States, epicenters of transmission have been linked closely to above-average summer temperatures. In particular, the strain of West Nile in the US spreads better during heat waves, and the spread of West Nile westward was correlated with unseasonable warmth. High temperatures are also to blame for the virus jumping from one species of mosquito to a much more urban-loving one, leading to outbreaks across the US.… Record-breaking incidences of West Nile are strongly linked to global climate patterns and the direct effects of carbon dioxide emissions.
In 2010, the world experienced the hottest year since records have been kept, and ended the
hottest decade ever measured. Last year, 2012, broke even more high temperature records.
October 2012 was the 332nd month in a row when global temperatures were above the twentieth-century average. The worst drought since the Dust Bowl of the 1930s ravaged crops and dried up water supplies in many communities. Many farmers have already been forced to adjust to the drying of soil. The lack of water has caused a buildup of
toxins in corn and other crops unable to process nitrogen fertilizer.
In order to pinpoint the difference between global warming and natural variability, Dr. James Hansen, the single most influential climate expert in the scientific community, produced with two of his colleagues, Makiko Sato and Reto Ruedy,
a groundbreaking statistical analysis of extreme temperatures all over the world from the years 1951 through 2010 that compared the more normal baseline period of 1951 through 1980 to more recent decades, 1981 through 2010, and especially the last several years when the impacts of global warming have been more prominently manifested, 1981 through 2010.
By breaking down the surface temperatures of almost the entire world into blocks of 150 square miles each, Hansen was able to calculate the frequency of extremely high temperatures (and all other temperatures) during the last sixty years. The results—which do not rely on climate models, climate science, or any theories of causation—demonstrate clearly that there has been up to a 100-fold increase in extreme high temperatures in recent years compared to earlier decades. The statistical analysis shows that in the last several years, extreme temperatures have been occurring regularly on approximately 10 percent of the Earth’s surface, while during the earlier decades such events occurred
on only 0.1 to 0.2 percent of the Earth’s surface.
Hansen’s chosen metaphor to explain the difference consists of two dice, each with the requisite six sides. The first die, which shows the range of temperatures over the years between 1951 and 1980, has two sides representing “normal” seasons, two other sides representing “warmer than normal” seasons, and the final two sides representing “cooler than normal” seasons. That used to be the “normal” distribution of temperatures. The second die, however, showing the range of temperatures in more recent years, has only one side representing a normal season and only one side representing a cooler than normal season, but three sides representing warmer than normal seasons and the remaining side now representing
extremely hot
seasons—
seasons that are way outside the boundary of the statistical range that used to prevail.
In the language of statisticians, a standard deviation quantifies how far the range, or spread, of a particular set of phenomena differs from the average spread. Extreme—in this case, either unusually hot or unusually cold—seasons naturally occur far less frequently than average or near-average seasons. Because seasons with extreme temperatures used
to be so much less frequent, they nevertheless often surprised us, even though they fell within the normally expected range. Seasons that are
three
standard deviations from the average were exceedingly rare, but still did occur from time to time as part of the normal range.
The average temperature is warmer overall even though extremely cold events still continue to occur, though rarely. In other words, the entire distribution of temperatures has moved to much warmer values, and the bell curve of distribution has widened and flattened slightly, so that there is much more temperature variability than used to occur. But the most significant finding is that the
frequency of extremely hot temperatures has gone up dramatically.
Hansen infers that the cause is global warming—and indeed, these results turn out to be perfectly consistent with what global warming science has long predicted. (In voluminous other studies, Hansen and climate scientists around the world have proven causality to a degree judged “unequivocal” and “indisputable” by virtually all of the world’s scientific community.) But the results themselves are based on observations of real temperatures in the real world. They cannot be argued with, and the implications are powerfully clear.
As the old saying has it in Tennessee, if you see a turtle on top of a fence post, it is highly likely that it didn’t get there by itself.
*
And now we are seeing turtles on every tenth fence post in every field in the world. They didn’t get there on their own. It is now abundantly obvious that all the extreme temperatures and the extreme weather events associated with them are like turtles on a fence post. They didn’t happen without human interference in the climate.
In 2012, new World Bank president Jim Yong Kim released a study showing
temperatures will likely rise by 4 degrees C (7.2 degrees F) without bolder steps to reduce CO
2
, and that there is
“no certainty that adaptation to a 4 degree world is possible.” Gerald Meehl, of the National Center for Atmospheric Research, uses a different metaphor to explain what is happening: if a baseball player who takes steroids hits a home run, it’s possible that he might have hit the home run even without the steroids. But the fact that he took the illegal performance-enhancing drug makes it much more likely
that he will hit a home run in his next at bat. Within Meehl’s metaphor, the 90 million tons of global warming pollution that we are putting into the atmosphere every twenty-four hours are like steroids for the climate. An innovative 2012 study of the previous decade’s climate predictions showed that the “
worst case” future projections are the ones most likely to occur.
The increases in the global average temperature and the greater frequency of extremely high temperatures that Hansen and others are documenting are also melting all of the ice-covered regions of the Earth. Only thirty years ago, the Arctic Ocean was almost completely covered by ice in summer as well as winter. Remember? Some called it the North Polar Ice Cap. Tell your grandchildren how it used to separate Eurasia from North America and the Atlantic from the Pacific all year round. Last year’s record low in the volume and the area it covered marked an acceleration of a melting pattern that has led to a
49 percent loss in three decades and could, in the view of many ice scientists, produce a
100 percent loss in as little as a decade.
Some shipping companies are excited that the fabled Northern Sea Route is now open for several months a year.
A Chinese ship, the
Snow Dragon
, traversed the North Pole to Iceland and back in the summer of 2012. A high-speed fiber optic cable is now being installed to link the Tokyo stock markets with their counterparts in New York City
so that computer-driven trades can be executed more quickly. Fishing fleets are preparing to exploit the rich biological resources of the
Arctic Ocean, which until now have been protected by the ice. Navies from some countries are discussing the
movement of military assets into the region, though discussions have also begun on the possibility of agreements to foster the peaceful resolution of issues involving the safety, sovereignty, and development of the Arctic Ocean as it becomes ice-free in summer.