Observed temperature changes
Main article: Instrumental temperature record
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Earth has been in radiative imbalance since at least the 1970s, where less energy leaves the atmosphere than enters it. Most of this extra energy has been absorbed by the oceans.[28] It is very likely that human activities substantially contributed to this increase in ocean heat content.[29]
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Two millennia of mean surface temperatures according to different reconstructions from climate proxies, each smoothed on a decadal scale, with the instrumental temperature record overlaid in black.
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NOAA graph of Global Annual Temperature Anomalies 1950–2012, showing the El Niño-Southern Oscillation
The global average (land and ocean) surface temperature shows a warming of 0.85 [0.65 to 1.06] °C in the period 1880 to 2012, based on multiple independently produced datasets.[30] Earth's average surface temperature rose by 0.74±0.18 °C over the period 1906–2005. The rate of warming almost doubled for the last half of that period (0.13±0.03 °C per decade, versus 0.07±0.02 °C per decade).[31]
The average temperature of the lower troposphere has increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Climate proxies show the temperature to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.[32]
The warming that is evident in the instrumental temperature record is consistent with a wide range of observations, as documented by many independent scientific groups.[33] Examples include sea level rise, because sea water expands as it warms (thermal expansion),[34] widespread melting of snow and land ice,[35] increased heat content of the oceans,[33] increased humidity,[33] and the earlier timing of spring events,[36] e.g., the flowering of plants.[37] The probability that these changes could have occurred by chance is virtually zero.[33]
Observed temperature changesMain article: Instrumental temperature recordrefer to caption and image descriptionEarth has been in radiative imbalance since at least the 1970s, where less energy leaves the atmosphere than enters it. Most of this extra energy has been absorbed by the oceans.[28] It is very likely that human activities substantially contributed to this increase in ocean heat content.[29]refer to caption and adjacent textTwo millennia of mean surface temperatures according to different reconstructions from climate proxies, each smoothed on a decadal scale, with the instrumental temperature record overlaid in black.refer to caption and adjacent textNOAA graph of Global Annual Temperature Anomalies 1950–2012, showing the El Niño-Southern OscillationThe global average (land and ocean) surface temperature shows a warming of 0.85 [0.65 to 1.06] °C in the period 1880 to 2012, based on multiple independently produced datasets.[30] Earth's average surface temperature rose by 0.74±0.18 °C over the period 1906–2005. The rate of warming almost doubled for the last half of that period (0.13±0.03 °C per decade, versus 0.07±0.02 °C per decade).[31]The average temperature of the lower troposphere has increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Climate proxies show the temperature to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.[32]The warming that is evident in the instrumental temperature record is consistent with a wide range of observations, as documented by many independent scientific groups.[33] Examples include sea level rise, because sea water expands as it warms (thermal expansion),[34] widespread melting of snow and land ice,[35] increased heat content of the oceans,[33] increased humidity,[33] and the earlier timing of spring events,[36] e.g., the flowering of plants.[37] The probability that these changes could have occurred by chance is virtually zero.[33]
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