Quick Answers to Tough Questions About Climate Change

Two degrees Fahrenheit. That’s roughly how much Earth’s average temperature has risen since the 1880s. It may not sound like much, but the change is having effects all over the globe: Ice is melting at the North and South poles. Ocean levels are rising. In some places, rainfall is getting heavier; in others, droughts are becoming more severe. 

This increase in Earth’s average temperature over a long period of time is called global warming. The increase along with all its side effects are known as climate change. Scientists have linked climate change to human activities.    

Some people remain unconvinced that humans are causing the warming or that it’s even happening. In a 2016 Pew Research Center survey, 20 percent of Americans said there’s no solid proof of global warming. But the vast majority of climate scientists—97 percent, according to studies by the Center for Climate Change Communication at George Mason University in Virginia—agree that the problem is real and urgent. If dramatic steps aren’t taken, they say, life on Earth could become very challenging.

“It’s difficult to make people understand how urgent this is when you look outside and the weather seems pretty normal,” says James Hansen, a climate scientist at Columbia University in New York City.

Here’s what you need to know about the causes and effects of climate change and what can be done about it.

Two degrees Fahrenheit. That’s roughly how much Earth’s average temperature has risen since the 1880s. It may not sound like much, but the change is having effects all over the globe. Ice 

is melting at the North and South poles. Ocean levels are rising. In some places, rainfall is getting heavier. In others, droughts are becoming more severe.

This increase in Earth’s average temperature over a long period of time is called global warming. The increase along with all its side effects are known as climate change. Scientists have linked climate change to human activities.

Some people remain unconvinced that humans are causing the warming. Some even doubt that it’s happening. In a 2016 Pew Research Center survey, 20 percent of Americans said there’s no solid proof of global warming. But the vast majority of climate scientists agree that the problem is real and urgent. In fact, 97 percent agree, according to studies by the Center for Climate Change Communication at George Mason University in Virginia. If dramatic steps aren’t taken, they say, life on Earth could become very challenging.

“It’s difficult to make people understand how urgent this is when you look outside and the weather seems pretty normal,” says James Hansen, a climate scientist at Columbia University in New York City.

Here’s what you need to know about the causes and effects of climate change and what can be done about it.

Greenhouse gases are invisible gases in the air that act like the glass panes of a greenhouse, trapping some of the sun’s heat close to Earth. Some of them, such as carbon dioxide, occur naturally in our atmosphere. But when we burn fossil fuels (such as coal and oil) to power homes, cars, and factories, we release even more greenhouse gases.

The so-called greenhouse effect is a good thing—to some extent. Without it, our planet would be a frozen wasteland. The problem, climate scientists say, is that we’re producing too much of these greenhouse gases. Since the Industrial Revolution, the amount of carbon dioxide in the atmosphere has increased by more than 40 percent. That means more heat is being trapped and, as a result, Earth’s average temperature has been rising.

Greenhouse gases are invisible gases in the air that act like the glass panes of a greenhouse. They trap some of the sun’s heat close to Earth. Some of them, such as carbon dioxide, occur naturally in our atmosphere. But when we burn fossil fuels (such as coal and oil) to power homes, cars, and factories, we release even more greenhouse gases.

The so-called greenhouse effect is a good thing—to some extent. Without it, our planet would be a frozen wasteland. The problem, climate scientists say, is that we’re producing too much of these greenhouse gases. Since the Industrial Revolution, the amount of carbon dioxide in the atmosphere has increased by more than 40 percent. That means more heat is being trapped. As a result, Earth’s average temperature has been rising.

Experts have examined the natural factors known to affect Earth’s temperature and concluded that these factors are not changing nearly enough to cause the current warming. Carbon dioxide levels did rise and fall naturally long ago, but those changes occurred gradually over thousands of years. Now, through the burning of fossil fuels, humans are releasing carbon dioxide into the air much faster than nature has ever done, scientists say. That explains the rapid warming better than anything else, most climate scientists have concluded.  

Experts have examined the natural factors known to affect Earth’s temperature. They’ve concluded that these factors are not changing nearly enough to cause the current warming. Carbon dioxide levels did rise and fall naturally long ago. But those changes occurred gradually over thousands of years. Now, humans are releasing carbon dioxide into the air much faster than nature has ever done, scientists say. And they’re doing that by burning fossil fuels. That explains the rapid warming better than anything else, most climate scientists have concluded.

To understand how cold weather occurs in a warming world, it helps to know the difference between climate and weather. Weather is what’s going on outside in a certain place on any given day. It can change quickly and be hard to predict. Climate describes what weather conditions are usually like in a place over a prolonged period of time—and it changes slowly. Scientists say that Earth’s climate has been getting hotter for decades (see “Tracking the Warming Trend,” below).

“Two weeks of really cold temperatures don’t negate decades of warming,” says Jake Crouch of the National Oceanic and Atmospheric Administration (NOAA).

In Canada, for example, winters are still bitterly cold—but not as consistently cold as they used to be. The warming trend means that the ice in the country’s outdoor skating rinks is melting earlier in the season. Researchers estimate that the number of outdoor ice-skating days will drop by 34 percent in Toronto and 19 percent in Calgary by 2090.

To understand how cold weather occurs in a warming world, it helps to know the difference between climate and weather. Weather is what’s going on outside in a certain place on any given day. It can change quickly and be hard to predict. Climate describes what weather conditions are usually like in a place over a prolonged period of time. It changes slowly. Scientists say that Earth’s climate has been getting hotter for decades.

“Two weeks of really cold temperatures don’t negate decades of warming,” says Jake Crouch of the National Oceanic and Atmospheric Administration (NOAA).

In Canada, for example, winters are still bitterly cold. But they’re not as consistently cold as they used to be. The warming trend means that the ice in the country’s outdoor skating rinks is melting earlier in the season. Researchers estimate that the number of outdoor ice-skating days will drop by 34 percent in Toronto and 19 percent in Calgary by 2090.

Scientists have published strong evidence that the warming trend is making heat waves more frequent and intense. Coastal flooding is also increasing as the oceans rise. As for hurricanes and other storms, while global warming doesn’t necessarily cause them, it likely makes them worse. For example, during Hurricane Harvey last August, up to 40 percent more rain poured down than would have if the exact same hurricane had happened decades earlier, experts say.

Climate change, says Kathleen Hayhoe, a climate scientist at Texas Tech University, “takes the natural risks that we’ve always faced and exacerbates them.”

Scientists have published strong evidence that the warming trend is making heat waves more frequent and intense. Coastal flooding is also increasing as the oceans rise. As for hurricanes and other storms, while global warming doesn’t necessarily cause them, it likely makes them worse. For example, during Hurricane Harvey last August, up to 40 percent more rain poured down than would have if the exact same hurricane had happened decades earlier, experts say.

Climate change, says Kathleen Hayhoe, a climate scientist at Texas Tech University, “takes the natural risks that we’ve always faced and exacerbates them.” 

Sea water levels are rising for two main reasons, scientists say. The oceans are getting warmer—and water expands as it heats up, causing sea levels to rise. Plus, melting glaciers and ice sheets are adding more water to the oceans.

The seas are now rising at an average rate of about 1 foot per century. If that were to continue, the increase would probably be manageable, some experts say. But some scientists fear sea levels could begin to rise much more quickly. Ultimately, seas could rise 20 feet or more above their current level. That’s enough to flood many of the world’s biggest coastal cities, such as New York, Miami, and Shanghai. But just how long it would take to happen is unclear. Our best bet, experts say, is to try to slow the process of sea level rise by cutting emissions.

Sea water levels are rising for two main reasons, scientists say. The oceans are getting warmer—and water expands as it heats up, causing sea levels to rise. Plus, melting glaciers and ice sheets are adding more water to the oceans.

The seas are now rising at an average rate of about 1 foot per century. If that were to continue, the increase would probably be manageable, some experts say. But some scientists fear sea levels could begin to rise much more quickly. Ultimately, seas could rise
20 feet or more above their current level. That’s enough to flood many of the world’s biggest coastal cities, such as New York, Miami, and Shanghai. But just how long it would take to happen is unclear. Our best bet, experts say, is to try to slow the process of sea level rise by cutting emissions.

People around the world are already feeling the effects. In Cape Town, South Africa, for example, years of warmer weather—coupled with less rainfall—have led to three straight years of drought. The city of 4 million people now faces a water shortage so extreme that its water supply could run out in 2019.

In other places, too much water is the problem. Because of sea level rise, the Marshall Islands in the Pacific Ocean flood frequently and could be unfit for human habitation within decades, scientists say. 

If greenhouse gas levels continue to rise unchecked, the impacts could be much more severe.

Over the next 25 or 30 years, scientists say, the climate is likely to continue to warm, causing more extreme weather, including stronger hurricanes, more prolonged droughts, and more wildfires. In the long term, climate effects could become so severe that they lead to political unrest in some places and mass extinctions of plants and animals.

People around the world are already feeling the effects. In Cape Town, South Africa, for example, there’s been less rainfall. This, coupled with years of warmer weather, has led to three straight years of drought. The city of 4 million people now faces a water shortage so extreme that its water supply could run out in 2019.

In other places, too much water is the problem. Because of sea level rise, the Marshall Islands in the Pacific Ocean flood frequently. They could be unfit for human habitation within decades, scientists say.

If greenhouse gas levels continue to rise unchecked, the impacts could be much more severe.

Over the next 25 or 30 years, scientists say, the climate is likely to continue to warm. That will cause more extreme weather. This includes stronger hurricanes, more prolonged droughts, and more wildfires. In the long term, climate effects could become so severe that they lead to political unrest in some places. They might even lead to mass extinctions of plants and animals.

Most climate scientists say it’s too late for the warming to be stopped altogether, but it can be slowed to a potentially manageable pace—if humans drastically reduce greenhouse gas emissions. Some countries, such as Sweden, have already seen their emissions fall after investing in renewable energy. Other countries have set emissions limits for power plants. But experts say we need to do much more to avoid the worst effects of climate change.

Nearly all 196 countries have signed a 2016 climate pact known as the Paris agreement, pledging to voluntarily limit future greenhouse gas emissions. The goal is to keep Earth’s temperature from rising more than 3.6 degrees Fahrenheit this century. That would “hold warming to something we actually can largely adapt to without fundamental changes and impacts on our civilization,” says Hayhoe, the climate scientist. 

Most climate scientists say it’s too late for the warming to be stopped altogether. But it can be slowed to a potentially manageable pace. That is, if humans drastically reduce greenhouse gas emissions. Some countries, such as Sweden, have already seen their emissions fall after investing in renewable energy. Other countries have set emissions limits for power plants. But experts say we need to do much more to avoid the worst effects of climate change.

Nearly all 196 countries have signed a 2016 climate pact known as the Paris agreement. These nations have pledged to voluntarily limit future greenhouse gas emissions. The goal is to keep Earth’s temperature from rising more than 3.6 degrees Fahrenheit this century. That would “hold warming to something we actually can largely adapt to without fundamental changes and impacts on our civilization,” says Hayhoe, the climate scientist. 

Last year, President Trump said that the U.S.—the second-largest greenhouse gas emitter after China—would withdraw from the Paris agreement. Trump said the pact imposes unfair environmental standards on American businesses and could hurt the economy, including the loss of 2.7 million jobs by 2025.

“The bottom line is that the Paris accord is very unfair, at the highest levels, to the United States,” Trump said.

However, under the rules of the deal, the soonest any country can drop out is November 4, 2020. In the meantime, the Trump administration is reversing policies—such as increased vehicle fuel efficiency standards and limits on pollution at power plants—designed to reduce U.S. emissions and meet the goals of the Paris agreement. Trump says these requirements were unfairly burdensome to car and energy companies.

But at the same time, a growing number of U.S. cities, businesses, and universities have pledged to reduce greenhouse gas emissions on their own in order to help meet the Paris objectives. 

The U.S. is the second-largest greenhouse gas emitter after China. Last year, President Trump said that the U.S. would withdraw from the Paris agreement. Trump said the pact imposes unfair environmental standards on American businesses and could hurt the economy, including the loss of 2.7 million jobs by 2025.

“The bottom line is that the Paris accord is very unfair, at the highest levels, to the United States,” Trump said.

However, under the rules of the deal, the soonest any country can drop out is November 4, 2020. In the meantime, the Trump administration is reversing policies designed to reduce U.S. emissions and meet the goals of the Paris agreement. This includes policies like increased vehicle fuel efficiency standards and limits on pollution at power plants. Trump says these requirements were unfairly burdensome to car and energy companies.

But at the same time, a growing number of U.S. cities, businesses, and universities have pledged to reduce greenhouse gas emissions on their own. They’re aiming to help meet the Paris objectives. 

Yes, and those alternative energy sources may end up being cheaper than burning fossil fuels, some scientists say. Wind turbines, solar panels, hydroelectric dams, and nuclear power plants produce among the fewest emissions. But converting to such power sources would be more expensive now, and it would be disruptive while we make the transition. Ultimately, however, the shift to renewable energy sources could pay for itself by reducing climate change and health problems associated with air pollution, although that isn’t certain.

Yes, and those alternative energy sources may end up being cheaper than burning fossil fuels, some scientists say. Wind turbines, solar panels, hydroelectric dams, and nuclear power plants produce among the fewest emissions. But converting to such power sources would be more expensive now. It also would be disruptive while we make the transition. Ultimately, however, the shift to renewable energy sources could pay for itself. The switch could reduce climate change and health problems associated with air pollution, although that isn’t certain.

A lot, actually. You can cut your own emissions by opting to walk, bike, or use public transportation instead of driving. If you need to drive, pick a small, fuel-efficient car.  

If enough people change their behavior, it could make a difference, says Maria Zuber, who directs the climate action plan at the Massachusetts Institute of Technology.

“I think young people have an extremely important role to play here,” she says. “So many of them really want to leave this world in a better place than the world they came into. Realizing how motivated and dedicated these kids are gives me hope.”

A lot, actually. You can cut your own emissions by opting to walk, bike, or use public transportation instead of driving. If you need to drive, pick a small, fuel-efficient car.

If enough people change their behavior, it could make a difference, says Maria Zuber. She directs the climate action plan at the Massachusetts Institute of Technology.

“I think young people have an extremely important role to play here,” she says. “So many of them really want to leave this world in a better place than the world they came into. Realizing how motivated and dedicated these kids are gives me hope.”

With reporting by Laura Anastasia, Tricia Culligan, and by The New York Times.

With reporting by Laura Anastasia, Tricia Culligan, and by The New York Times.