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An Atlas of the Global Water Cycle

An Atlas of the Global Water Cycle: Based on the IPCC AR4 Climate Models OPEN ACCESS

Wee Ho Lim
Michael L. Roderick
Copyright Date: 2009
Published by: ANU Press
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  • Book Info
    An Atlas of the Global Water Cycle
    Book Description:

    What do climate models predict for the rainfall where you live? What about evaporation or runoff? Should your local community consider constructing new dams or do the existing water storages appear adequate? What about the availability of water for irrigation farming? Do the predictions differ between different climate models or do all the models basically predict the same changes in water availability where you live? These are all simple questions but it is surprisingly hard for an individual, whether they be a farmer, water resources engineer, teacher or interested citizen, to answer them. As researchers active in the field we could not answer the questions either. In fact, we had never seen a compilation of the rainfall, evaporation and runoff predictions made by all the different climate models. The Atlas contains maps and tables that document model predictions contributed by international climate modelling groups to the 2007 4th Assessment Report of the Intergovernmental Panel on Climate Change. The predictions are made available here via the wonders of the internet and ongoing cooperation by the international climate modelling community who routinely archive their results. The maps and tables in the Atlas document rainfall, evaporation and runoff estimates for the 20th century along with predictions of the same quantities at the end of the 21st century. Whatever your interest, we hope you find the Atlas as helpful as we do.

    eISBN: 978-1-921536-89-2
    Subjects: Aquatic Sciences
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Table of Contents

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  1. There is much discussion in the scientific literature and concern in the wider community about changing water availability associated with the enhanced greenhouse effect. That is not surprising – water is essential for life on earth.

    What will happen to water availability in the future? Will it remain the same or will it change?

    If models predict declining precipitation should dryland agricultural industries begin relocation to suitable regions where the models predict increasing precipitation?

    Are the current urban water supplies sufficient to meet the expected demand or do we need to plan for increased storage or perhaps construct desalinisation plants?


  2. 2 Methods (pp. 3-4)

    Grids containing monthly climate model output for precipitation, evaporation and near-surface air temperature were downloaded from the multi-model climate data archive Output from 20 models were downloaded for the historic period known as the 20C3M scenario (20th Century Model Runs) and for two future scenarios known as the A1B and A2 scenarios. The future scenarios assume an emissions trajectory with the A1B scenario based on mid-range emissions while the A2 scenario assumes a higher level of emissions (see Appendix for details). In some cases, multiple runs from a given model were available and these were analysed individually. The number...

  3. 3 Results (pp. 5-290)

    Maps and tables are shown in Section 3.1. The maps use model output from the 20C3M and A1B scenarios. We used the A1B scenario to ensure consistency with the IPCC maps and related theoretical research (Held and Soden 2006).

    Precipitation time series for the 20th century (20C3M) and for the 21st century (A1B) for each model run are shown in Section 3.2. In that section we show time series for the globe and for the Australian continent. The Bureau of Meteorology (2008) observations for the Australian continent are also plotted enabling a visual comparison between model simulations and observations.


  4. 4 Discussion (pp. 291-292)

    The main points to emerge were:

    (a) Of the 39 model runs examined, the globally averaged precipitation for 1970-1999 varied from 916.5 to 1187.2 mm per year and was close to the widely quoted (but as yet unmeasured) value of 1000 mm per year for global precipitation (Section 3.3).

    (b) All 39 model runs showed steadily increasing global precipitation over the next 100 years for the A1B scenario. This is of course equal to the increase in evaporation. The increase in annual precipitation for the A1B scenario by the end of the 21st century simulated by the 39 model runs...