Global Climate Change
What's the difference between climate change and global warming?
"Global warming" refers to the long-term warming of the planet. "Climate change" encompasses global warming, but refers to the broader range of changes that are happening to our planet, including rising sea levels; shrinking mountain glaciers; accelerating ice melt in Greenland, Antarctica and the Arctic; and shifts in flower/plant blooming times.
What's the difference between weather and climate?
"Weather" refers to the more local changes in the climate we see around us, on short timescales from minutes to hours to days to weeks. Examples are familiar - rain, snow, clouds, winds, thunderstorms, heat waves and floods. "Climate" refers to longer-term averages (they may be regional or global), and can be thought of as the weather averaged over several seasons, years or decades.
How is Earth's sea ice faring in our warming world?
Arctic sea ice volume (the amount of three-dimensional space the sea ice occupies) and extent (how much sea ice covers the Arctic Ocean) have been declining since record-keeping began in the late 1970's and prior. Additionally, Antarctic sea ice extent is currently below the long-term average of prior decades since 1979, when scientists started keeping track.
Are the land-based ice sheets in Greenland and Antarctica continuing to lose mass (ice)?
Data from NASA's GRACE satellites, which measured Earth's gravity field, show that the land ice sheets in both Antarctica and Greenland have been losing mass (ice) since 2002. Both ice sheets have seen an acceleration of ice mass loss since 2009.
Is the ozone hole causing climate change?
False-color view of total ozone over the Antarctic pole. Purple and blue represent areas where there is the least ozone, yellows and reds where there is more ozone. Credit: NASA Ozone Hole Watch. Yes and no. The ozone hole is basically a man-made hole in the ozone layer above the South Pole during the Southern Hemisphere's spring. The ozone layer, which lies high up in the atmosphere, shields us from harmful ultraviolet (UV) rays that come from the Sun. Unfortunately we punched a hole in it, through the use of gases like chlorofluorocarbons (CFCs) in spray cans and refrigerants, which break down ozone molecules in the upper atmosphere. While some extra of the Sun's UV rays slip through the ozone hole, their net effect is to cool the stratosphere more than they warm the troposphere. So this increase in UV rays cannot explain the global warming of the planet's surface. What scientists have uncovered recently, however, is that the ozone hole has been affecting climate in the Southern Hemisphere. That's because ozone is also a powerful greenhouse gas, and destroying it has made the stratosphere (the second layer of the atmosphere going upwards) over the Southern Hemisphere colder. The colder stratosphere has resulted in faster winds near the pole, which somewhat surprisingly can have impacts all the way to the equator, affecting tropical circulation and rainfall at lower latitudes. The ozone hole is not causing global warming, but it is affecting atmospheric circulation.
Is it too late to prevent climate change? Humans have caused major climate changes to happen already, and we have set in motion more changes still. Even if we stopped emitting greenhouse gases today, global warming would continue to happen for at least several more decades, if not centuries.
Humans have caused major climate changes to happen already, and we have set in motion more changes still. Even if we stopped emitting greenhouse gases today, global warming would continue to happen for at least several more decades, if not centuries.
How do we know what greenhouse gas and temperature levels were in the distant past?
Ice cores are scientists' best source for historical climate data. Other tools for learning about Earth's ancient atmosphere include growth rings in trees, which keep a rough record of each growing season's temperature, moisture and cloudiness going back about 2,000 years. Corals also form growth rings that provide information about temperature and nutrients in the tropical ocean. Other proxies, such as benthic cores, extend our knowledge of past climate back about a billion years into the past.
What's NASA got to do with climate change? s.
NASA's role is to make observations of our Earth system that can be used by the public, policymakers and to support strategic decisions. Its job is to do rigorous science. However, the agency does not promote particular climate policies.
What happens if the next solar cycle becomes less active? Will we go into a new ice age?
No. Even if the amount of radiation coming from the Sun were to decrease as it has before, it would not significantly affect the global warming coming from long-lived, human-emitted greenhouse gases. Further, given our greenhouse gas emissions to date and those expected to come, the evidence points to the next "ice age" being averted altogether.
Is the Sun causing global warming?
No. The Sun can influence Earth's climate, but it isn't responsible for the warming trend we've seen over the past few decades.
How are Earth's mountain glaciers faring in a warming world?
On average, most of Earth's mountain glaciers are continuing to melt. Scientists know this by calculating the glaciers' "average mass balance": taking accumulated snowfall on those glaciers and subtracting ice losses due to melting, meltwater runoff (drainage away from glaciers) and evaporation (when a liquid turns into a gas). Their calculations show decades of more ice losses than gains.
Which measurement is more accurate: taking Earth's surface temperature from the ground or from space?
Since satellites technically measure neither temperature nor the surface (where people live), it's safe to say that ground thermometers are more accurate than satellite measurements.
What is the greenhouse effect and how does it work?
The greenhouse effect is the way in which heat is trapped close to the surface of the Earth by "greenhouse gases." These heat-trapping gases can be thought of as a blanket wrapped around the Earth, which keeps it toastier than it would be without them. Greenhouse gases include carbon dioxide, methane and nitrous oxides. Greenhouse gases arise naturally, and are part of the make-up of our atmosphere. Earth is sometimes called the "Goldilocks" planet - it's not too hot, not too cold, and the conditions are just right to allow life, including us, to flourish. Part of what makes Earth so amenable is the naturally-arising greenhouse effect, which keeps the planet at a friendly 15 °C (59 °F) on average. But in the last century or so, humans have been interfering with the energy balance of the planet, mainly through the burning of fossil fuels that give off additional carbon dioxide into the air. The level of carbon dioxide in Earth's atmosphere has been rising consistently for decades and traps extra heat near the surface of the Earth, causing temperatures to rise
Why does the temperature record shown on your "Vital Signs" page begin at 1880?
Three of the world's most complete temperature tracking records - from NASA's Goddard Institute for Space Studies, the National Oceanic and Atmospheric Administration's National Climactic Data Center and the UK Meteorological Office's Hadley Centre - begin in 1880. Prior to 1880, temperature measurements were made with instruments like thermometers. The oldest continuous temperature record is the Central England Temperature Data Series, which began in 1659, and the Hadley Centre has some measurements beginning in 1850, but there are too few data before 1880 for scientists to estimate average temperatures for the entire planet.
What do volcanoes have to do with climate change?
What do volcanoes have to do with climate change? Overall, volcanoes release less than 2 percent of the equivalent amount of CO2 released by human activities. Quite small.
Can you explain the urban heat island effect?
While urban areas are warmer than surrounding rural areas, the urban heat island effect has had little to no effect on our warming world, because scientists have accounted for it in their measurements.
Has Earth continued to warm since 1998?
Yes, evidence shows warming from 1998 to the present, with the four most recent years (2014, 2015, 2016 and 2017) being the four warmest years globally since 1880.
Is the ocean continuing to warm?
Yes, the ocean is continuing to warm. Notably, all ocean basins have been experiencing significant warming since 1998, with more heat being transferred deeper into the ocean since 1990. To date, the ocean contains 93 percent of the heat from human-induced global warming, and the year 2017 was the global ocean's warmest year ever measured.
Do scientists agree on climate change?
Yes, the vast majority of actively publishing climate scientists - 97 percent - agree that humans are causing global warming and climate change.
