In addition to our surface station data, we have many different lines of evidence that Earth is warming ( learn more). When different teams of climate scientists in different agencies (e.g., NOAA and NASA) and in other countries (e.g., the U.K.’s Hadley Centre) average these data together, they all find essentially the same result: Earth’s average surface temperature has risen by about 1.8☏ (1.0☌) since 1880. We know the world is warming because people have been recording daily high and low temperatures at thousands of weather stations worldwide, over land and ocean, for many decades and, in some locations, for more than a century. Since 1750, humans have increased the abundance of carbon dioxide in the atmosphere by nearly 50 percent. A net 5 billion metric tons of human-produced carbon remain in the atmosphere each year, raising the global average carbon dioxide concentrations by about 2.3 parts per million per year. Of this human-produced carbon, forests and other vegetation absorb around 3.2 billion metric tons per year, while the ocean absorbs about 2.5 billion metric tons per year. Among these, carbon dioxide is of greatest concern to scientists because it exerts a larger overall warming influence than the other gases combined.Īt present, humans are putting an estimated 9.5 billion metric tons of carbon into the atmosphere each year by burning fossil fuels, and another 1.5 billion through deforestation and other land cover changes. Carbon dioxide, methane, nitrous oxide, ozone, and various chlorofluorocarbons are all human-emitted heat-trapping gases. Virtually all climate scientists agree that this increase in heat-trapping gases is the main reason for the 1.8☏ (1.0☌) rise in global average temperature since the late nineteenth century. Yes, by increasing the abundance of greenhouse gases in the atmosphere, human activities are amplifying Earth’s natural greenhouse effect. It is easy to conclude our world is warming even without the GHCN data. Perhaps most compelling reason: Mother Nature herself offers many lines of corroborating evidence that our world is warming-from melting ice sheets and glaciers, to the rising global sea level, to the earlier arrival of spring and longer warm seasons, to plant and animal species migrations.No reasons have been found to question the integrity or the quality of the GHCN dataset. Both the temperature data record and NOAA’s analyses of the temperature data have been peer-reviewed by other, independent teams of scientists in the U.S.NOAA is open and transparent about its quality control measures and anyone can read all about them in the published literature or on the NOAA website. NOAA uses quality control measures to ensure the temperature data are of the highest quality and accuracy for research purposes.Yes, we can trust the Global Historical Climatology Network (GHCN) data for three key reasons:
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