Climate Change Research Program Japanese

Core Project3. Assessment of climate risk based on integrated climate, impact, and land use models

Research Plan > Core Research Projects > 2010 Research Results

[2010 Research Results]

Global warming impact and change in ecosystem services

Global warming is likely to influence terrestrial ecosystems such as forest and grassland in various manners. This will occur not only in wild organisms but also in human societies through the changes in ecosystem functions related to provisional and regulating ecosystem services. We have developed a terrestrial ecosystem model simulating ecological processes (called VISIT), aiming at assessing the impact of global warming on ecosystems and their services under changing environments. It has been realized that future global environmental change can bring about severe risks by decreasing ecosystem services.

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Global warming impact and change in ecosystem services (img)

Terrestrial ecosystems have a climate regulation service, which is determined by the net budget of greenhouse gases (i.e., CO2, CH4, and N2O). We used the VISIT model to estimate the change in the climate regulation service during the last 110 years, taking into account atmospheric change and land-use conditions. It was found that greenhouse gas budget occurred heterogeneously over the land surface (A), such that CH4 and/or N2O could play a dominant role (B). Since the 1950s, elevated atmospheric CO2 concentrations have stimulated plant photosynthesis, leading to increased uptake into ecosystems (C). On the other hand, emissions of methane and nitrous oxide have also increased as a result of cropland expansion, implying the importance of continuous assessment of these greenhouse gas budgets.

Constraining future climate change projections of the multi-model using multivariate technique

Many climate models have projected global warming in the future. However, the projected global warming includes uncertainties such as different amount and spatial features of the surface temperature increase. To reduce the uncertainties, future projections need to be constrained by the assessment of reliability in the simulated results. In this study, we analyzed the relationship between the simulated late 20th century climate and future projections, using the multivariate technique. Using the relationship and observed climate data, we estimated future changes in surface temperature. The estimated surface temperature changes indicate the possibility of a higher surface temperature change in the future than the change estimated by the multi-model mean.

Estimation of future change in surface temperature by considering the statistical relationship between simulated climate and future projections
Estimation of future change in surface temperature by considering the statistical relationship between simulated climate and future projections

The black lines and numbers in the map show the estimation of future surface temperature change using the statistical relationship between the results of climate models and the late 20th century climate data. Values indicated by colors show the difference between the estimated change and the equal-weighted mean change of the multi-model. The difference is statistically significant at the 95% level. The unit is K. The figure shows that the estimated surface temperature changes are higher globally, particularly in the northern higher-latitude region, than the equal-weighted mean change of the multi-model.

Projection of changes in world maize productivity considering the uncertainty of the climate scenario

We conducted impact projection simulations in which the climate projection information with multiple climate models were input into the global crop production model to estimate the impact of climate change on the change in maize productivity while considering the uncertainty of the climate projection information.
When we assumed that future greenhouse gas emissions followed the SRES-A2 scenario (diverse society, large emission), the average maize productivity in the top 13 countries in the world by the 2080s was expected to decrease greatly in most climate projecti on information. However, no big change or only a slight increase was predicted in four models. In addition, the uncertainty range of the productivity change was shown to grow larger with time in the simulation period.

Uncertainty of the mean productivity change of maize by 14 GCMs based on the SRES A2 scenario
Uncertainty of the mean productivity change of maize by 14 GCMs based on the SRES A2 scenario

This graph shows the rate of change in world maize productivity assuming the climate projection information of 14 climate models based on the SRES A2 scenario.
The average rate of change of productivity was predicted with −6.8% (uncertainty range: −26%–+12%) in the 2020s, −12.4% (uncertainty range: −33%–+15%) in the 2050s, and −22% (uncertainty range: −52%–+10%) in the 2080s. The 1990s served as the base period for comparison.

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