Vital Climate Graphics - Update

RISING TEMPERATURES

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It’s getting hot in here

The global average surface temperature has increased over the 20th century by about 0.6 degrees Celsius. This increase in temperature is likely to have been the largest for any century in the last 1000 years.

Departures in temperature in °C (from the 1990 value)

Evidence from tree ring records, used to re- construct temperatures over this period, sug- gests that the 1990s was the warmest period in a millennium. It is very likely that nearly all land areas will warm more rapidly than the global average, particularly those at high northern latitudes in the cold season. There are very likely to be more hot days; fewer cold days, cold waves, and frost days; and a reduced diurnal tem- perature range.

Global instrumental observations

Several models all SRES envelope

Observations, Northern Hemisphere, proxy data

Projections

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Variations of the Earth’s surface temperature: year 1000 to year 2100

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Comparison between modeled and observed temperature since 1860

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Temperature anomalies in °C

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Bars show the range in year 2100 produced by several models

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Natural causes

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Scenarios

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A1B A1T A1FI

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A2 B1 B2 IS92a

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UnitedNationsEnvironmentProgramme /GRID-Arendal

After 1950, the temperature rise cannot be explained by natural causes alone.

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1850

1900

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2000

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Man made causes

Natural versus man made There is new and stronger evidence that most of the warm- ing observed over the last 50 years is attributable to human activities. It is unlikely that the warming is to be entirely natural. Reconstructions of climate data from the last 1,000 years also indicate that this 20th century warming was un- usual and unlikely to be the response to natural forcing alone. Volcanic eruptions and variation in solar irradiance do not explain the warming in the latter half of the 20th century, but they may have contributed to the observed warming in the first half. As we can see frommodels of temperature changes caused by natural forcing, we should have observed a decrease in the global average temperature lately, but we have not. We have observed an increase.

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This temperature increase cannot be explained by human activity alone.

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1850

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Natural and man made causes

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The model that includes man made and natural causes is the best fit.

Model results Observations

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United Nations Environment Programme / GRID-Arendal