Background
According to the authors, "greenhouse gas warming simulations generally show increased intensity of Asian summer monsoonal circulations (e.g., Meehl and Washington, 1993; Hirakuchi and Giorgi, 1995; Li et al., 1995; Zwiers and Kharin, 1998; Chakraborty and Lal, 1994; Suppiah, 1995; Zhao and Kellog, 1988; Hulme et al., 1998; Wang, 1994)," as is also the case for Northern Australia during the austral summer season (Whetton et al., 1993, 1994; Suppiah, 1995).  They also say that much the same thing would likely be predicted for the African monsoons, "given that the tropical atmospheric moisture content, latent heating and overall hydrological cycle have been hypothesized to increase with increasing tropospheric temperature (e.g., IPCC, 1996)."

What was done
To test this hypothesis of the climate modeling community, Chase et al. examined changes in several independent intensity indices of the four major tropical monsoonal circulations over the period 1950-1998, or over the last half of what climate alarmists refer to as the past millennium's most dramatic century of warming, which includes the highly contentious final two decades of the 20th century that are supposed to represent truly "unprecedented" global warming.

What was learned
In each of the four regions examined, the authors report finding "diminished monsoonal circulations over the period of record," as well as "evidence of diminished spatial maxima in the global hydrological cycle since 1950."  In addition, they say that "trends since 1979, the period of strongest reported surface warming, do not indicate any change in monsoon circulations."

What it means
In the words of the authors, current state-of-the-art models of the climate system "generally simulate a strong relationship between globally averaged warming and increasing extremes in the hydrological cycle including monsoonal strength."  However, after a careful analysis of real-world meteorological observations, they report that "we find no evidence to support this model hypothesis in these data."  Once again, therefore, the best climate models yet devised fail to even qualitatively describe what is happening in the world of nature.

References
Chakraborty, B. and Lal, M.  1994.  Monsoon climate and its change in a doubled CO2 atmosphere simulated by CSIRO9 model.  TAO 5: 515-536.

Hirakuchi, H. and Giorgi, F.  1995.  Multiyear present-day and 2xCO2 simulations of monsoon climate over eastern Asia and Japan with a regional climate model nested in a general circulation model.  Journal of Geophysical Research 100: 21,105-21,125.

Hulme, M., Osborn, T.J. and Johns, T.C.  1998.  Precipitation sensitivity to global warming: Comparison of observations with HADCM2 simulations.  Geophysical Research Letters 25: 3379-3382.

IPCC (Intergovernmental Panel on Climate Change).  1996.  Climate Change 1995.  Cambridge University Press, Cambridge, UK.

Li, X., Yang, S., Zhao, Z. and Ding, Y.  1995.  The future climate change simulation in east Asia from CGCM experiments.  Quarterly Journal of Applied Meteorology 6: 1-8.

Meehl, G.A. and Washington, W.M.  1993.  South Asian summer monsoon variability in a model with doubled atmospheric carbon dioxide concentration.  Science 260: 1101-1104.

Suppiah, R.  1995.  The Australian summer monsoon: CSIRO9 GCM simulations for 1xCO2 and 2xCO2 conditions.  Global and Planetary Change 11: 95-109.

Wang, H.  1994.  The monsoon precipitation variation in the climate change.  Acta Meteorologie Sinica 9: 48-56.

Whetton, P.H., Fowler, A.M., Haylock, M.R. and Pittock, A.B.  1993.  Implications of climate change due to the enhanced greenhouse effect on floods and droughts in Australia.  Climatic Change 25: 289-317.

Whetton, P.H., Rayner, P.J., Pittock, A.B. and Haylock, M.R.  1994.  An assessment of possible climate change in the Australian region based on an intercomparison of general circulation modeling results.  Journal of Climate 7:441-463.

Zhao, Z. and Kellogg, W.W.  1988.  Sensitivity of soil moisture to doubling of carbon dioxide in climate model experiments, Pt. 2, Asian monsoon region.  Journal of Climate 1: 367-378.

Zwiers, F.W. and Kharin, V.V.  1998.  Changes in the extremes of the climate simulated by the CCC GCM2 under CO2 doubling.  Journal of Climate 11: 2200-2222.