Climate Change: Models, Scenarios, Climate Impacts. Models overview Accuracy – Uncertainty Scenarios Impacts. How would you model climate?. What components would you include? What about human factors? Limitations? How do test if you’re right?. Climate Models.
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Climate Change: Models, Scenarios, Climate Impacts
Ocean general circulation models (OGCMs)
An OGCM is the ocean counterpart of an AGCM
It is a three-dimensional representation of the ocean and sea ice.
OGCMs are useful by themselves for studying ocean circulation, interior processes and variability, but they depend on being supplied with data about surface air temperature and other atmospheric properties.
Carbon cycle models
The terrestrial carbon cycle is modeled within the land surface scheme of the AGCM, and the marine carbon cycle within the OGCM. T
Needed in order to capture several important climate feedbacks on carbon dioxide concentration, for instance fertilization of plant growth by carbon dioxide and uptake or outgassing of carbon dioxide by the oceans.
Atmospheric chemistry models
The Hadley Centre has developed a three-dimensional global atmospheric chemistry model called STOCHEM.
The chemical scheme is designed to include the main agents responsible for the production and destruction of ozone and methane in the lower atmosphere.
Met Office Hadley Center Model
Goddard Institute for Space Studies (GISS)
Observed precipitation anomaly (top panel), the model generated precipitation anomaly with SST forcing only (middle panel), and the model generated precipitation anomaly with the effects of observed SSTs and the added dust source (bottom panel).
Model w/SST only
Observed w/SST and dust via land use
A dust storm strikes Powers County, Colorado, in April 1935
A climate model can be used to simulate the temperature changes that occur both from natural and anthropogenic causes. The simulations represented by the band in:
From (b), it can be seen that inclusion of
anthropogenic forcings provides a plausible
explanation for a substantial part of the observed
temperature changes over the past century, but
the best match with observations is obtained in (c)
when both natural and anthropogenic factors are
These results show that the forcings
included are sufficient to explain the observed
changes, but do not exclude the possibility that
other forcings may also have contributed. The
bands of model results presented here are for four
runs from the same model. Similar results to those
in (b) are obtained with other models with
The climate models, far from being melodramatic, may be conservative in the predictions they produce. For example, here’s a graph of sea level rise:
Here, the models have understated the problem. In reality the events are all within the upper range of the model’s predictions.
Inability after some 30 years of research to understand the likely climate response in the tropics and in polar regions is a major reason for uncertainty in climate change consequences.
For the same scenario of future greenhouse gas increases, climate models differ by a factor of two in terms of their predicted warming in both regions.
This has obvious implications for our ability to predict events in the tropics, such as hurricanes and drought, and at high latitudes, such as sea ice and ice sheet melting (with sea level rise).
The Geophysical Fluid Dynamics Laboratory
(GFDL) model tended to produce half the tropical
warming reported in the Goddard Institute for Space Studies (GISS) model as a result CO2 input differences;
On the other hand, its high latitude sensitivity was about doubled
Nakicenovic et al. 2000
A schematic representation of the SRES scenario family. The A1 and A2 families have a more economicfocus than B1 and B2, which are more environmental, whilst the focus of A1 and B1 is more global compared to the more regional A2 and B2.
The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.
The B1 scenarios describe a convergent world with the same global population that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource-efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.
The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.
Source: 4th Assessment WG2 SPM
Annual mean temperature change, 2071 to 2100 relative to 1990: Global Average in 2085 = 3.1oC
Annual mean precipitation change: 2071 to 2100 Relative to 1990
This massive “red tide” of the dinoflagellate Noctiluca stretched for more than 20 miles along the southern California coast. Non-toxic blooms such as these can cause extensive mortalities of plants and animals in shallow waters when the bloom biomass decays, stripping oxygen from the water. (Photo by P. Franks)
Maldives is made up of a chain of 1190 small coral islands that are grouped into 26 atolls (80 islands resorts and 200 inhabited islands)
France heat wave death toll set at 14,802
Maximal temperature in the Paris area, excess emergency department visits (grey bars), and hospital admissions (white bars) in the Assistance Publique–Hôpitaux de Paris, 1–30 August 2003.
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