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Climate Change Science:�Temperature Projections and Observations

Richard B. Rood

January 2019

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Projected Global Temperature Trends: 2100

2071-2100 temperatures relative to 1961-1990.

Special Report on Emissions Scenarios Storyline B2 (middle of the road warming).

IPCC 2001

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Observed Temperature Anomaly 2015-2019�https://data.giss.nasa.gov/gistemp/maps/index_v4.html

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Global temperature anomaly: thru 2019�https://www.giss.nasa.gov/research/news/20200115/

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Note: There is

consistency from many models, many scenarios, that there will be warming. (1.5 – 5.5 C)

IPCC 2001

Clarify the red line. In some of these figures it seems these are observations – this one? In some the past is model simulation. Likewise, what is the range – the range of observations, or the range of models. Again, in this one, the range seems to be observations because of the jumps.

Uncertainty: Observations

Scenarios, wide uncertainty on the right.

Internal variability, wiggles

Model, range from any one scenario.

There are no scenarios with temperature decline.

At 2100, they are are still rising. Some more slowly than others.

This is a remarkable opportunity. We have knowledge, with a high degree of confidence, what is likely to happen in the future. Have looked at the past, projections of future. Introduced observational uncertainty, model uncertainty, scenario uncertainty, and internal or natural variability.

Figure 9-1b: Variations of the Earth’s surface temperature: years 1000 to 2100. Over the period 1000 to 1860, observations are shown of variations in average surface temperature of the Northern Hemisphere (corresponding data from the Southern Hemisphere not available) constructed from proxy data (tree rings, corals, ice cores, and historical records). The line shows the 50-year average, and the grey region the 95% confidence limit in the annual data. From the years 1860 to 2000, observations are shown of variations of global and annual averaged surface temperature from the instrumental record. The line shows the decadal average. Over the period 2000 to 2100, projections are shown of globally averaged surface temperature for the six illustrative SRES scenarios and IS92a as estimated by a model with average climate sensitivity. The grey region “several models all SRES envelope” shows the range of results from the full range of 35 SRES scenarios in addition to those from a range of models with different climate sensitivities.

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IPCC (2007) projections for the next 100 years

Note: From one IPCC assessment to the next, there is no fundamental change in sign and range.

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Some questions?

Why do the poles warm more quickly?
Why are the north and south poles different?
Why are land and oceans different?
What is the IPCC?
What are the sources of uncertainty?
Is this adequate for planning?
What is a model?