Frequently Asked Questions

“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.

“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, sleet, and hail.

“Climate” refers to longer-term averages (which may be regional or global) and can be thought of as the weather averaged over several decades.

Humans have caused major climate changes to happen already, and we have set in motion more changes still. However, if we stopped emitting greenhouse gases today, the rise in global temperatures would begin to flatten within a few years. Temperatures would then plateau but remain well-elevated for many, many centuries.

Yes, the vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.

NASA’s role is to make observations of our Earth's systems (geosphere, biosphere, cryosphere, hydrosphere, and atmosphere)--and how they connect--that can be used by the public, researchers, policymakers and to support strategic decisions. Its job is to perform rigorous science. However, the agency does not promote particular climate policies.

Climate researchers use every possible direct and indirect measurement to study the full history of Earth's climate, from the latest satellite observations to samples of prehistoric ice extracted from glaciers.

Modern observations mostly come from weather stations, weather balloons, radars, ships and buoys, and satellites.

No. To understand why not, imagine you're a nurse checking a patient's chart. You find the following temperature readings (Fahrenheit) for the last few hours: 99.2, 99.8, 1000, 101.4. You'd know immediately that the third number was a mistake. To make a realistic assessment of the patient's condition, you'd have to either adjust it or throw it out.

Not yet. They have to be adjusted to account for all the changes that happen over time. Read on to learn more about those changes.

Major climate research organizations worldwide have developed mathematically rigorous, peer-reviewed data-processing methods to identify and compensate for changes in observing conditions.

The records of global temperatures calculated by U.S. and other major climate research organizations are remarkably similar, despite the different data-processing techniques used. The techniques used by NASA's Goddard Institute for Space Studies (GISS), National Climatic Data Center (NCDC), and other respected groups are peer-reviewed, and the processed data sets have undergone many peer-reviewed analyses as well.

Almost half of the National Oceanic and Atmospheric Administration's (NOAA) corrected data are cooler than the original records. NOAA's corrections of temperatures over the oceans — done to compensate for changes in methods of observing the temperature of water at the surface of the ocean — reduced the warming trend in global temperature.

No, the original records are preserved and are available at no cost online. You can access the National Climatic Data Center's (NCDC) U.S. and global records here.

The greenhouse effect is the way in which heat is trapped close to Earth's surface by “greenhouse gases.”

The amount of anthropogenic carbon dioxide (CO₂) absorbed by Earth's life forms, ocean, and other "sinks" might decrease as time goes by. Natural carbon sinks (the carbon absorbers, as opposed to "sources," which release carbon) on land and in the ocean have become less effective over time. That is, natural sinks that removed about 60% of annual human-caused CO₂ emissions in 1959 now remove about 55% today.

Contrary to common belief, it’s cow belching due to enteric fermentation.

Since MOXIE works by ingesting carbon dioxide – the gas that’s mostly driving climate change here on Earth – and produces oxygen, a lot of people wondered whether it could it be helpful on our own planet. But while technology is part of any plan for addressing climate change, the conversion that MOXIE accomplished on Mars is not a viable approach.

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.

Yes, evidence shows warming from 1998 to the present, with 2014, 2015, 2016, 2017, 2018, 2019, and 2020 being the hottest years globally since 1880.

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.

​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.

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.

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.

On average, most of Earth’s mountain glaciers are continuing to melt.

Arctic sea ice volume and extent have been declining since record-keeping began in the late 1970s and prior. Antarctic sea ice extent is currently below the long-term average of prior decades since 1979.

Surface mass balance is the difference between the precipitation (rain and snow) that has accumulated on the upper surfaces of glaciers and ice sheets and what has been lost due to melt and eventual runoff and evaporation.

Total mass balance is the difference between total mass gains and total mass losses, which includes ice lost in the lower margins due to calving and thinning from contact with warm ocean waters.

Melting land ice, like mountain glaciers and the Greenland and Antarctic ice sheets, will change Earth’s rotation only if the meltwater flows into the ocean. For example, if the Greenland ice sheet were to completely melt and the meltwater were to completely flow into the ocean, then global sea level would rise by about seven meters (23 feet) and Earth would rotate more slowly, with the length of the day becoming longer than it is today, by about 2 milliseconds.

Melting sea ice, such as the Arctic ice cap, does not change sea level because the ice displaces its volume and, hence, does not change Earth’s rotation.

No. The Sun can influence Earth’s climate, but it isn’t responsible for the warming trend we’ve seen in recent decades.

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.

Volcanic eruptions are often discussed in relation to climate change because they release CO₂ (and other gases) into our atmosphere. However, human contributions to the carbon cycle are more than 100 times those from all the volcanoes in the world - combined.

In comparison, while volcanic eruptions do cause an increase in atmospheric CO₂, human activities emit a Mount St. Helens-sized eruption of CO₂ every 2.5 hours and a Mount Pinatubo-sized eruption of CO₂ twice daily.

Yes and no. The ozone hole is not causing global warming, but it is affecting atmospheric circulation.

The amount of carbon dioxide (CO₂) in the atmosphere is measured by many different methods, all around the world. By using more than one approach, scientists can be sure they’re measuring a global trend, rather than a local variation.

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.

It depends on the style you’re using. Read on for a few examples.

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