Q:
What causes global warming?
A: Global
warming occurs when carbon dioxide (CO2) and other air pollutants collect in
the atmosphere and absorb sunlight and solar radiation that have bounced off
the earth’s surface. Normally, this radiation would escape into space—but these
pollutants, which can last for years to centuries in the atmosphere, trap the
heat and cause the planet to get hotter.
In the United States, the burning of
fossil fuels to make electricity is the largest source of heat-trapping
pollution, producing about two billion tons of CO2 every year. Coal-burning
power plants are by far the biggest polluters. The country’s second-largest
source of carbon pollution is the transportation sector, which generates about
1.7 billion tons of CO2 emissions a year.
Curbing dangerous climate change
requires very deep cuts in emissions, as well as the use of alternatives to
fossil fuels worldwide. The good news is that we’ve started a turnaround: CO2
emissions in the United States actually decreased from 2005 to 2014, thanks in
part to new, energy-efficient technology and the use of cleaner fuels. And
scientists continue to develop new ways to modernize power plants, generate
cleaner electricity, and burn less gasoline while we drive. The challenge is to
be sure these solutions are put to use and widely adopted.
Q:
Is the earth really getting hotter?
A: Yes.
Over the past 50 years, the average global temperature has increased at the
fastest rate in recorded history. And experts see the trend is accelerating:
All but one of the 16 hottest years in NASA’s 134-year record have
occurred since 2000.
Climate change deniers have argued
that there has been a “pause” or a “slowdown” in rising global temperatures,
but several recent studies, including a 2015 paper published in the journal Science, have
disproved this claim. And scientists say that unless we curb global-warming
emissions, average U.S. temperatures could increase by up to 10 degrees
Fahrenheit over the next century.
Q:
Is global warming causing extreme weather?
A: Scientists
agree that the earth’s rising temperatures are fueling longer and hotter heat
waves, more frequent droughts, heavier rainfall, and more powerful hurricanes.
In 2015, for example, scientists said that an ongoing drought in California—the
state’s worst water shortage in 1,200 years—had been intensified by 15 percent
to 20 percent by global warming. They also said the odds of similar droughts
happening in the future had roughly doubled over the past century. And in 2016,
the National Academies of Science, Engineering, and Medicine announced that
it’s now possible to confidently attribute certain weather events, like some
heat waves, directly to climate change.
The earth’s ocean temperatures are
getting warmer, too—which means that tropical storms can pick up more energy.
So global warming could turn, say, a category 3 storm into a more dangerous
category 4 storm. In fact, scientists have found that the frequency of North
Atlantic hurricanes has increased since the early 1980s, as well as
the number of storms that reach categories 4 and 5. In 2005, Hurricane
Katrina—the costliest hurricane in U.S. history—struck New Orleans; the
second-costliest, Hurricane Sandy, hit the East Coast in 2012.
The impacts of global warming are
being felt across the globe. Extreme heat waves have caused tens of thousands of
deaths around the world in recent years. And in an alarming sign of events to
come, Antarctica has been losing about 134 billion metric tons of ice per year
since 2002. This rate could speed up if we keep burning fossil fuels at our
current pace, some experts say, causing sea levels to rise several meters over
the next 50 to 150 years.
Q:
Why should I care?
A: Each
year, scientists learn more about how global warming is affecting the planet,
and many agree that environmental, economic, and health consequences are likely
to occur if current trends continue. Here’s just a smattering of what we can
look forward to:
- Melting glaciers, early snowmelt, and severe droughts will cause more dramatic water shortages and increase the risk of wildfires in the American West.
- Rising sea levels will lead to coastal flooding on the Eastern Seaboard, especially in Florida, and in other areas such as the Gulf of Mexico.
- Forests, farms, and cities will face troublesome new pests, heat waves, heavy downpours, and increased flooding. All those factors will damage or destroy agriculture and fisheries.
- Disruption of habitats such as coral reefs and Alpine meadows could drive many plant and animal species to extinction.
- Allergies, asthma, and infectious disease outbreaks will become more common due to increased growth of pollen-producing ragweed, higher levels of air pollution, and the spread of conditions favorable to pathogens and mosquitoes.
