an introduction to climate change

An Introduction to Climate ChangeWhat it could mean to you and your family

Climate change is changing our economy, health and communities in diverse ways. Scientists warn that if we do not aggressively curb climate change now, the results will likely be disastrous.

The Basics

Carbon dioxide and other global warming pollutants are collecting in the atmosphere like a thickening blanket, trapping the sun's heat and causing the planet to warm up.

Although local temperatures fluctuate naturally, over the past 50 years the average global temperature has increased at the fastest rate in recorded history. Scientists say that unless we curb the emissions that cause climate change, average U.S. temperatures could be 3 to 9 degrees higher by the end of the century.

The United States Global Change Research Program (which includes the Department of Defense, NASA, National Science Foundation and other government agencies) has said that "global warming is unequivocal and primarily human-induced" and that "climate changes are underway in the United States and are projected to grow."

Q:

What causes global warming?A:

Carbon dioxide and other air pollution that is collecting in the atmosphere like a thickening blanket, trapping the sun's heat and causing the planet to warm up. Coal-burning power plants are the largest U.S. source of carbon dioxide pollution -- they produce 2.5 billion tons every year. Automobiles, the second largest source, create nearly 1.5 billion tons of CO2 annually.

Here's the good news: technologies exist today to make cars that run cleaner and burn less gas, modernize power plants and generate electricity from nonpolluting sources, and cut our electricity use through energy efficiency. The challenge is to be sure these solutions are put to use.

Q:

Is the earth really getting hotter?A:

Yes. Although local temperatures fluctuate naturally, over the past 50 years the average global temperature has increased at the fastest rate in recorded history. And experts think the trend is accelerating: the 10 hottest years on record have all occurred since 1990. Scientists say that unless we curb

global warming emissions, average U.S. temperatures could be 3 to 9 degrees higher by the end of the century.

Q:

Are warmer temperatures causing bad things to happen?A:

Global warming is already causing damage in many parts of the United States. In 2002, Colorado, Arizona and Oregon endured their worst wildfire seasons ever. The same year, drought created severe dust storms in Montana, Colorado and Kansas, and floods caused hundreds of millions of dollars in damage in Texas, Montana and North Dakota. Since the early 1950s, snow accumulation has declined 60 percent and winter seasons have shortened in some areas of the Cascade Range in Oregon and Washington.

Of course, the impacts of global warming are not limited to the United States. In 2003, extreme heat waves caused more than 20,000 deaths in Europe and more than 1,500 deaths in India. And in what scientists regard as an alarming sign of events to come, the area of the Arctic's perennial polar ice cap is declining at the rate of 9 percent per decade.

Q:

Is global warming making hurricanes worse?A:

Global warming doesn't create hurricanes, but it does make them stronger and more dangerous. Because the ocean is getting warmer, tropical storms can pick up more energy and become more powerful. So global warming could turn, say, a category 3 storm into a much more dangerous category 4 storm. In fact, scientists have found that the destructive potential of hurricanes has greatly increased along with ocean temperature over the past 35 years.

Q:

Is there really cause for serious concern?A:

Yes. Global warming is a complex phenomenon, and its full-scale impacts are hard to predict far in advance. But each year scientists learn more about how global warming is affecting the planet, and many agree that certain consequences are likely to occur if current trends continue. Among these:

Melting glaciers, early snowmelt and severe droughts will cause more dramatic water shortages in the American West.

Rising sea levels will lead to coastal flooding on the Eastern seaboard, in Florida, and in other areas, such as the Gulf of Mexico.

Warmer sea surface temperatures will fuel more intense hurricanes in the southeastern Atlantic and Gulf coasts.

Forests, farms and cities will face troublesome new pests and more mosquito-borne diseases.

Disruption of habitats such as coral reefs and alpine meadows could drive many plant and animal species to extinction.

Q:

What country is the largest source of global warming pollution?A:

The United States. Though Americans make up just 4 percent of the world's population, we produce 25 percent of the carbon dioxide pollution from fossil-fuel burning -- by far the largest share of any country. In fact, the United States emits more carbon dioxide than China, India and Japan, combined. Clearly America ought to take a leadership role in solving the problem. And as the world's top developer of new technologies, we are well positioned to do so -- we already have the know-how.

Q:

How can we cut global warming pollution?A:

It's simple: By reducing pollution from vehicles and power plants. Right away, we should put existing technologies for building cleaner cars and more modern electricity generators into widespread use. We can increase our reliance on renewable energy sources such as wind, sun and geothermal. And we can manufacture more efficient appliances and conserve energy.

Q:

Why aren't these technologies more commonplace now?A:

Because, while the technologies exist, the corporate and political will to put them into widespread use does not. Many companies in the automobile and energy industries put pressure on the White House and Congress to halt or delay new laws or regulations -- or even to stop enforcing existing rules -- that would drive such changes. From requiring catalytic converters to improving gas mileage, car companies have fought even the smallest measure to protect public health and the environment. If progress is to be made, the American people will have to demand it.

Q:

Do we need new laws requiring industry to cut emissions of global warming pollution?

A:

Yes. Voluntary reduction programs have failed to stop the growth of emissions. Even leaders of major corporations, including companies such as DuPont, Alcoa and General Electric, agree that it's time for the federal government to create strong laws to cut global warming pollution. Public and political support for solutions has never been stronger. Congress is now considering fresh proposals to cap emissions of carbon dioxide and other heat-trapping pollutants from America's largest sources -- power plants, industrial facilities and transportation fuels.

Stricter efficiency requirements for electric appliances will also help reduce pollution. One example is the 30 percent tighter standard now in place for home central air conditioners and heat pumps, a Clinton-era achievement that will prevent the emission of 51 million metric tons of carbon -- the equivalent of taking 34 million cars off the road for one year. The new rule survived a Bush administration effort to weaken it when, in January 2004, a federal court sided with an NRDC-led coalition and reversed the administration's rollback.

Q:

Is it possible to cut power plant pollution and still have enough electricity?

A:

Yes. First, we must use more efficient appliances and equipment in our homes and offices to reduce our electricity needs. We can also phase out the decades-old, coal-burning power plants that generate most of our electricity and replace them with cleaner plants. And we can increase our use of renewable energy sources such as wind and sun. Some states are moving in this direction: California has required its largest utilities to get 20 percent of their electricity from renewable sources by 2017, and New York has pledged to compel power companies to provide 25 percent of the state's electricity from renewable sources by 2013.

Q:

How can we cut car pollution?A:

Cost-effective technologies to reduce global warming pollution from cars and light trucks of all sizes are available now. There is no reason to wait and hope that hydrogen fuel cell vehicles will solve the problem in the future. Hybrid gas-electric engines can cut global warming pollution by one-third or more today; hybrid sedans, SUVs and trucks from several automakers are already on the market.

But automakers should be doing a lot more: They've used a legal loophole to make SUVs far less fuel efficient than they could be; the popularity of these vehicles has generated a 20 percent increase in transportation-related carbon dioxide pollution since the early 1990s. Closing this loophole and

requiring SUVs, minivans and pick-up trucks to be as efficient as cars would cut 120 million tons of carbon dioxide pollution a year by 2010. If automakers used the technology they have right now to raise fuel economy standards for new cars and light trucks to a combined 40 m.p.g., carbon dioxide pollution would eventually drop by more than 650 million tons per year as these vehicles replaced older models.

For more information on hybrid vehicles, see NRDC's hybrid guide.

Q:

What can I do to help fight global warming?A:

There are many simple steps you can take right now to cut global warming pollution. Make conserving energy a part of your daily routine. Each time you choose a compact fluorescent light bulb over an incandescent bulb, for example, you'll lower your energy bill and keep nearly 700 pounds of carbon dioxide out of the air over the bulb's lifetime. By opting for a refrigerator with the Energy Star label -- indicating it uses at least 15 percent less energy than the federal requirement -- over a less energy-efficient model, you can reduce carbon dioxide pollution by nearly a ton in total. Join NRDC in our campaign against global warming.

Q:

How can I argue with a global warming skeptic?A:

First, determine whether you're talking to a skeptic, or a denier. A genuine skeptic is someone who can be convinced by evidence, and the scientific evidence for human-caused global warming is overwhelming. (If you're dealing with a flat-earther, don't waste your breath.)

For detailed, point-by-point rebuttals to global warming naysayers, see Grist's How to Talk to a Climate Skeptic.

You should also consult New Scientist's Climate Change: A Guide for the Perplexed. It rounds up common climate myths and misperceptions.

If these resources don't answer your question, take a look at Real Climate, a blog by leading climate researchers that delves into climate science in great, and often technical, detail.

The Consequences of Global WarmingOn Weather PatternsHigher temperatures could lead to increased droughts and wildfires, heavier rainfall and a greater number of Category 4 and 5 hurricanes.

More Powerful and Dangerous Hurricanes

Warmer water in the oceans pumps more energy into tropical storms, making them stronger and potentially more destructive. Even with storms of the same intensity, future hurricanes will cause more damage as higher sea levels exacerbate storm surges, flooding, and erosion.

Warning signs today:

The number of category 4 and 5 storms has greatly increased over the past 35 years, along with ocean temperature.

Hurricane Katrina of August 2005 was the costliest and one of the deadliest hurricanes in U.S. history and caused economic losses in the order of $125 billion.

Drought and Wildfire

Warmer temperatures could increase the probability of drought. Greater evaporation, particularly during summer and fall, could exacerbate drought conditions and increase the risk of wildfires.


The 1999-2002 national drought was one of the three most extensive droughts in the last 40 years.

Warming may have lead to the increased drought frequency that the West has experienced over the last 30 years.

The 2006 wildland fire season set new records in both the number of reported fires as well as acres burned. Close to 100,000 fires were reported and nearly 10 million acres burned, 125 percent above the 10-year average.

Firefighting expenditures have consistently totaled upwards of $1 billion per year.

Intense Rainstorms

Warmer temperatures increase the energy of the climatic system and can lead to heavier rainfall in some areas. Scientists project that climate change will increase the frequency of heavy rainstorms, putting many communities at risk for devastation from floods. Check themap of flood vulnerability in the United States.


National annual precipitation has increased between 5 and 10 percent since the early 20th century, largely the result of heavy downpours.

The Intergovernmental Panel on Climate Change reports that intense rain events have increased in frequency during the last 50 years and human-induced global warming most likely contributed to the trend.

According to the National Oceanic and Atmospheric Administration, the Northeast region had its wettest summer on record in 2006, exceeding the previous record by more than 1 inch.

The Consequences of Global WarmingOn HealthHotter weather enables deadly mosquitoes to travel greater distances; carbon dioxide in the air aggravates asthma and allergies.

Deadly Heat Waves

More frequent and severe heat waves will result in a greater number of heat-related deaths.

http://www.nrdc.org/health/climate/floods.asp


In 2003, extreme heat waves claimed as many as 70,000 lives in Europe. In France alone, nearly 15,000 people died during two weeks of soaring temperatures, which reached as high as 104 degrees Fahrenheit.

Much of North America experienced a severe heat wave in July 2006, which contributed to the deaths of over 140 people, including some who owned working air conditioners.

In the 1995 Chicago heat wave, 739 heat-related deaths occurred in a one-week period.

Bad Air, Allergy and Asthma

Global warming could increase smog pollution in some areas and intensify pollen allergies and asthma. Hotter conditions could also aggravate local air quality problems, already afflicting more than 100 million Americans.


Scientific studies show that a higher level of carbon dioxide spurs an increase in the growth of weeds such as ragweed, whose pollen triggers allergies and exacerbates asthma.

The number of pollen allergy and asthma sufferers has increased worldwide over the last several decades. Some researchers have suggested that this could be an early health effect of human-caused climate change.

Air pollution makes allergies worse: Diesel exhaust particles can interact with pollen and deliver it deeper into the lung.

Rising temperatures increase ground-level ozone smog production, which presents a serious threat to asthmatics.

Infectious Disease and Food and Waterborne Illness Outbreaks

Warming temperatures, alternating periods of drought and deluges, and ecosystem disruption have contributed to more widespread outbreaks of infections like malaria, dengue fever, tick-borne encephalitis, and diarrheal illnesses. People living in poverty will be hardest hit by the global surge in infectious diseases.


Disease-carrying mosquitoes are spreading as the climate allows them to survive in formerly inhospitable areas. Mosquitoes that can carry dengue fever viruses were previously limited to elevations of 3,300 feet but recently appeared at 7,200 feet in the Andes Mountains of Colombia. Malaria has been detected in new higher-elevation areas in Indonesia and Africa, posing new risks to millions of impoverished people whose health is already challenged.

Heavy rainfall events can wash pathogens from contaminated soils, farms, and streets into drinking water supplies. An outbreak of diarrheal illness in Milwaukee in 1993 which affected 403,000 people was caused by the parasite Cryptosporidium, which washed into the city's drinking water supply after heavy rains.

Higher outdoor temperatures can cause increased outbreaks of foodborne illnesses such as salmonella, which reproduces more rapidly as temperatures increase. Another foodborne bacteria, Vibrio parahaemolyticus, once native to subtropical regions, has expanded its range as far north as Alaska, where in 2004 it sickened unlucky cruise ship passengers when they ate raw local oysters.

Dangerous Weather Events

A warmer atmosphere can hold -- and dump -- more moisture, contributing to more intense extreme weather events, which in turn put people's lives at risk.


Hurricane Katrina forced the evacuation of 1.7 million people in 2005, and lead to deaths and long-term health problems for 200,000 New Orleans residents.

A combination of rising sea levels, reduced snowfall and increased rainstorms threatens to flood the homes of 300,000 California residents in the Sacramento-San Joaquin river delta area, potentially contaminating the drinking water of 24 million people.

Alternating drought and floods have led to food and water shortages, malnutrition, mass migrations and international conflict. Some researchers suggest that 50 million people worldwide could become "environmental refugees" by 2010, displaced by rising sea levels, desertification, depleted aquifers and intermittent river flooding.

The Consequences of Global WarmingOn WildlifeRising temperatures ravage coral reefs and melt the habitats of polar bears and Antarctic penguins.

Ecosystem Shifts and Species Die-Off

Increasing global temperatures are expected to disrupt ecosystems, pushing to extinction those species that cannot adapt. The first comprehensive assessment of the extinction risk from global warming found that more than 1 million species could be obliterated by 2050 if the current trajectory continues.


A recent study of nearly 2,000 species of plants and animals discovered movement toward the poles at an average rate of 3.8 miles per decade. Similarly, the study found species in alpine areas to be moving vertically at a rate of 20 feet per decade in the second half of the 20th century.

The latest Intergovernmental Panel on Climate Change report found that approximately 20 to 30 percent of plant and animal species assessed so far are likely to be at increased risk of extinction if global average temperature increases by more than 2.7 to 4.5 degrees Fahrenheit.

Some polar bears are drowning because they have to swim longer distances to reach ice floes. The U. S. Geological Survey has predicted that two-thirds of the world's polar bear sub-populations will be extinct by mid-century due to melting of the Arctic ice cap.

In Washington's Olympic Mountains, sub-alpine forest has invaded higher elevation alpine meadows. Bermuda's mangrove forests are disappearing.

In areas of California, shoreline sea life is shifting northward, probably in response to warmer ocean and air temperatures.

Over the past 25 years, some Antarctic penguin populations have shrunk by 33 percent due to declines in winter sea-ice habitat.

The ocean will continue to become more acidic due to carbon dioxide emissions. Because of this acidification, species with hard calcium carbonate shells are vulnerable, as are coral reefs, which are vital to ocean ecosystems. Scientists predict that a 3.6 degree Fahrenheit increase in temperature would wipe out 97 percent of the world's coral reefs.

The Consequences of Global WarmingOn Glaciers and Sea LevelsArctic summers could be ice-free by 2040, and sea levels could rise as much as 23 inches by 2100 if current warming patterns continue.

Melting Glaciers, Early Ice Thaw

Rising global temperatures will speed the melting of glaciers and ice caps and cause early ice thaw on rivers and lakes.


After existing for many millennia, the northern section of the Larsen B ice shelf in Antarctica -- a section larger than the state of Rhode Island -- collapsed

between January and March 2002, disintegrating at a rate that astonished scientists. Since 1995, the ice shelf's area has shrunk by 40 percent.

According to NASA, the polar ice cap is now melting at the alarming rate of nine percent per decade. Arctic ice thickness has decreased 40 percent since the 1960s.

Arctic sea ice extent set an all-time record low in September 2007, with almost half a million square miles less ice than the previous record set in September 2005, according to the National Snow and Ice Data Center. Over the past 3 decades, more than a million square miles of perennial sea ice -- an area the size of Norway, Denmark and Sweden combined -- has disappeared.

Multiple climate models indicate that sea ice will increasingly retreat as the earth warms. Scientists at the U.S. Center for Atmospheric Research predict that if the current rate of global warming continues, the Arctic could be ice-free in the summer by 2040.

At the current rate of retreat, all of the glaciers in Glacier National Park will be gone by 2070.

Sea-Level Rise

Current rates of sea-level rise are expected to increase as a result both of thermal expansion of the oceans and melting of most mountain glaciers and partial melting of the West Antarctic and Greenland ice caps. Consequences include loss of coastal wetlands and barrier islands, and a greater risk of flooding in coastal communities. Low-lying areas, such as the coastal region along the Gulf of Mexico and estuaries like the Chesapeake Bay, are especially vulnerable.


Global sea level has already risen by 4 to 8 inches in the past century, and the pace of sea level rise appears to be accelerating. The Intergovernmental Panel on Climate Change predicts that sea levels could rise 10 to 23 inches by 2100, but in recent years sea levels have been rising faster than the upper end of the range predicted.

In the 1990s, the Greenland ice mass remained stable, but the ice sheet has increasingly declined in recent years. This melting currently contributes an estimated one-hundredth of an inch per year to global sea level rise.

Greenland holds 10 percent of the total global ice mass. If it melts, sea levels could increase by up to 21 feet.

an introduction to climate change

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