Global Warming

what is Ice Shelf

An ice shelf forms from the outflow of land ice and floats on the sea at the land’s edge. It creates a barrier that slows the flow of land ice into the ocean. In the last thirty years, both rapid disintegration of ice shelves and ice shelf collapses have been observed along Canada and the Antarctic Peninsula.

Global temperature

Global temperature is an average of air temperature recordings from weather stations on land and sea as well as some satellite measurements. Worldwide, 2006-2015 was the warmest decade on record since thermometer-based observations began nearly 150 years ago.

Carbon dioxide

Carbon dioxide is the gas that accounts for about 84 percent of total U.S. greenhouse gas emissions. In the U.S. the largest source of carbon dioxide (98 percent) emissions is combustion of fossil fuels. Combustion can be from mobile (vehicles) or stationary sources (power plants). As energy use increases, so do carbon dioxide emissions.

Biofuels

Biofuels are renewable fuels derived from biological materials, such as algae and plants, that can be regenerated. This distinguishes them from fossil fuels, which are considered nonrenewable. Example of biofuels are ethanol, methanol and biodiesel.

Methane

Methane is a gas and represents about 8 percent of total U.S. greenhouse gas emissions. The largest sources are wood burning in stoves and fireplaces, livestock digestive systems, and decomposition in landfills.

Greenhouse gases

The main greenhouse gases are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). Water vapor is the most plentiful at about one percent. The next most plentiful is carbon dioxide at 0.04 percent. The effect of human activity on global water vapor concentrations is too small to be important. The effects of human activity on the other greenhouse gases, however, is large and very important. These gases are increasing faster than they are removed from the atmosphere. Hydrologic cycle Hydrologic cycle is the process by which water moves around the earth. The cycle includes evaporation, precipitation, runoff, condensation, transpiration and infiltration.

Q: What is global warming? A: Here's a simple definition of global warming. (And yes, it's really happening.) 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: What causes global warming? A: Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gases 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. That's what's known as the greenhouse effect. 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: How is global warming linked to 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: What are the other effects of global warming? A: Each year, scientists learn more about the consequences of global warming, 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. Q: Where does the United States stand in terms of global-warming contributors? A: In recent years, China has taken the lead in global-warming pollution, producing about 28 percent of all CO2 emissions. The United States comes in second. Despite making up just 4 percent of the world’s population, we produce a whopping 16 percent of all global CO2 emissions—as much as the European Union and India (third and fourth place) combined. And America is still number one, by far, in cumulative emissions over the past 150 years. Our responsibility matters to other countries, and it should matter to us, too. Q: Is the United States doing anything to prevent global warming? A: We’ve started. But in order to avoid the worst effects of climate change, we need to do a lot more—together with other countries—to reduce our dependence on fossil fuels and start using clean energy instead. In 2015, the U.S. Environmental Protection Agency pledged to reduce carbon pollution from our power plants by nearly a third by 2030, relative to 2005 levels, through its Clean Power Plan. But fast-forward to 2017, and under the Trump Administration, the EPA proposed repealing this critical tool for curbing climate change. Likewise, while under the Obama administration, the U.S. Department of Transportation proposed carbon pollution and fuel economy standards intended to cut emissions through the 2020s, under Trump administration, the DOT is working to roll back those clean vehicle safeguards that protect the climate and our health. Fortunately, state leaders—including in car country itself—recognize that clean transportation must remain a priority if we are to address the costly risks of climate change and protect public health. And regional efforts around the country are helping to boost the electric car market, which saw an increase in sales for 2017 over 2016. Our clean energy economy is growing too, despite federal efforts to derail it. In 2016, wind employment grew by 32 percent and solar jobs increased by 25 percent. Globally, at the United Nations Conference on Climate Change in Paris, 195 countries—including the United States, at the time—agreed to pollution-cutting provisions with a goal of preventing the average global temperature from rising more than 1.5 degrees Celsius above preindustrial times. (Scientists say we must stay below a two-degree increase to avoid catastrophic climate impacts.) To help make the deal happen, the Obama administration pledged $3 billion to the Green Climate Fund, an international organization dedicated to helping poor countries adopt cleaner energy technologies. Under the terms of the Paris agreement, participating nations will meet every five years, starting in 2020, to revise their plans for cutting CO2 emissions. Beginning in 2023, they will also have to publicly report their progress. While in 2017, President Trump announced the country’s withdrawal from the Paris climate agreement and to eliminate “harmful and unnecessary policies such as the Climate Action Plan,” Americans are forging ahead without him. Through initiatives like the United States Climate Alliance, the Regional Greenhouse Gas Initiative, We Are Still In, and Climate Mayors, state, business, and local leaders have pledged to honor and uphold the goals of the Paris Agreement. More than 25 cities in 17 states, with populations totaling more than 5 million have adopted resolutions that will enable them to get 100 percent of their electricity from renewable sources like wind and solar. Even better, a new initiative by former New York City mayor Michael Bloomberg gives the urban layer of this movement a boost. He’s asked mayors from the 100 most populous cities in the country to share their plans for making their buildings and transportation systems run cleaner and more efficiently. The 20 that show the greatest potential for cutting the dangerous carbon pollution that’s driving climate change will share a total of $70 million in technical assistance funding provided by Bloomberg Philanthropies and partners. Q: Is global warming too big of a problem for me to help tackle? A: Wondering how to stop global warming? Reduce your own carbon footprint by following a few easy steps. Make conserving energy a part of your daily routine and your decisions as a consumer. When you shop for new appliances like refrigerators, washers, and dryers, look for products with the government’s Energy Star label; they meet a higher standard for energy efficiency than the minimum federal requirements. When you buy a car, look for one with the highest gas mileage and lowest emissions. You can also reduce your emissions by taking public transportation or carpooling when possible. And while new federal and state standards are a step in the right direction, much more needs to be done. Voice your support of climate-friendly and climate change preparedness policies, and tell your representatives that transitioning from dirty fossil fuels to clean power should be a top priority—because it’s vital to building healthy, more secure communities. Glaciers are melting, sea levels are rising, cloud forests are dying, and wildlife is scrambling to keep pace. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than at any time in the last 800,000 years. We often call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. While many people think of global warming and climate change as synonyms, scientists use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems—in part because some areas actually get cooler in the short term. Climate change encompasses not only rising average temperatures but also extreme weather events, shifting wildlife populations and habitats, rising seas, and a range of other impacts. All of those changes are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere, changing the rhythms of climate that all living things have come to rely on. What will we do—what can we do—to slow this human-caused warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the fate of the Earth as we know it—coasts, forests, farms, and snow-capped mountains—hangs in the balance. PHOTOS OF GLOBAL WARMING IM nowmelt and long, dry summers. The stresses on the park's flora are exacterbated by climate change. PHOTOGRAPH BY KEITH LADZINSKI, NAT GEO IMAGE COLLECTIONUNDERSTANDING THE GREENHOUSE EFFECT Understanding the greenhouse effect The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse, hence the name. TODAY’S POPULAR STORIES SCIENCE Fast food increases exposure to a 'forever chemical' called PFAS SCIENCE Huge new 'shark toothed' dinosaur found SCIENCE How Antarctica is melting from above and below Sunlight shines onto the Earth's surface, where the energy is absorbed and then radiate back into the atmosphere as heat. In the atmosphere, greenhouse gas molecules trap some of the heat, and the rest escapes into space. The more greenhouse gases concentrate in the atmosphere, the more heat gets locked up in the molecules. Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This natural greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees Fahrenheit (33 degrees Celsius) cooler. In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming. Levels of greenhouse gases have gone up and down over the Earth's history, but they had been fairly constant for the past few thousand years. Global average temperatures had also stayed fairly constant over that time—until the past 150 years. Through the burning of fossil fuels and other activities that have emitted large amounts of greenhouse gases, particularly over the past few decades, humans are now enhancing the greenhouse effect and warming Earth significantly, and in ways that promise many effects, scientists warn. Aren't temperature changes natural? Human activity isn't the only factor that affects Earth's climate. Volcanic eruptions and variations in solar radiation from sunspots, solar wind, and the Earth's position relative to the sun also play a role. So do large-scale weather patterns such as El Niño. But climate models that scientists use to monitor Earth’s temperatures take those factors into account. Changes in solar radiation levels as well as minute particles suspended in the atmosphere from volcanic eruptions, for example, have contributed only about two percent to the recent warming effect. The balance comes from greenhouse gases and other human-caused factors, such as land use change. The short timescale of this recent warming is singular as well. Volcanic eruptions, for example, emit particles that temporarily cool the Earth's surface. But their effect lasts just a few years. Events like El Niño also work on fairly short and predictable cycles. On the other hand, the types of global temperature fluctuations that have contributed to ice ages occur on a cycle of hundreds of thousands of years. For thousands of years now, emissions of greenhouse gases to the atmosphere have been balanced out by greenhouse gases that are naturally absorbed. As a result, greenhouse gas concentrations and temperatures have been fairly stable, which has allowed human civilization to flourish within a consistent climate. Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the Industrial Revolution. Changes that have historically taken thousands of years are now happening over the course of decades. Why does this matter? The rapid rise in greenhouse gases is a problem because it’s changing the climate faster than some living things can adapt to. Also, a new and more unpredictable climate poses unique challenges to all life.