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Monsoons (Models vs. Observations) -- Summary
Chase et al. (2003) report that "greenhouse gas warming simulations generally show increased intensity of Asian summer monsoonal circulations (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). In addition, they say that much the same would likely be predicted for African monsoons, "given that the tropical atmospheric moisture content, latent heating and overall hydrological cycle have been hypothesized to increase with increasing tropospheric temperature (IPCC, 1996)." Do real-world data substantiate this plethora of model-based predictions?

In broaching this question, Chase et al. studied changes in several intensity indices of the planet's four major tropical monsoonal circulations over the period 1950-1998, including the highly contentious final two decades of the 20th century that are claimed by climate alarmists to have experienced "unprecedented" global warming. For all four regions they report "diminished monsoonal circulations over the period of record," as well as evidence of "diminished spatial maxima in the global hydrological cycle since 1950." They also say that "trends since 1979, the period of strongest reported surface warming, do not indicate any change in monsoon circulations." Consequently, the models fail to even qualitatively describe what is happening in the world of nature with respect to monsoonal circulations.

In a related study spanning more than twice as many years (1871-2001), Kripalani et al. (2003) examined Indian monsoonal rainfall using observational data from the Indian Institute of Tropical Meteorology that were collected from 306 stations scattered across the country. In the course of this work they discovered decadal variations running through the record that revealed "distinct alternate epochs of above and below normal rainfall," which epochs tended to last for about three decades. In addition, they report "there is no clear evidence to suggest that the strength and variability of the Indian Monsoon Rainfall (IMR) nor the epochal changes are affected by the global warming," and they add that "studies by several authors in India have shown there is no statistically significant trend in IMR for the country as a whole."

Before concluding, Kripalani et al. note that "Singh (2001) investigated the long term trends in the frequency of cyclonic disturbances over the Bay of Bengal and the Arabian Sea using 100-year (1890-1999) data and found significant decreasing trends." As a result, they say "there seem[s] to be no support for the intensification of the monsoon nor any support for the increased hydrological cycle as hypothesized by [the] greenhouse warming scenario in model simulations." In addition, they report that "the analysis of observed data for the 131-year period (1871-2001) suggests no clear role of global warming in the variability of monsoon rainfall over India." Hence, the climate models strike out with respect to all of their Asian monsoon-related projections.

These several findings mirror the earlier discoveries of Kripalani and Kulkarni (2001), who studied summer monsoon (June-September) rainfall data from 120 east Asia stations for the period 1881-1998 and detected the presence of short-term variability in rainfall amounts on decadal and longer time scales, the longer "epochs" of which were found to last for about three decades over India and China and approximately five decades over Japan. Over the entire record, however, no significant long-term trends were observed. Hence, the observational history of summer rainfall trends throughout most of east Asia fails to support climate-alarmist claims of intensified monsoonal conditions in this region as a result of CO2-induced global warming.

In a paper that takes a much longer look at the characteristics of expanded African-Asian monsoon variability over the course of the entire Holocene, Overpeck and Webb (2000) found that large abrupt changes in monsoon moisture availability occurred multiple times throughout the past several thousand years, although they say that "a lack of research prevents precise reconstruction, explanation, or modeling of these changes." In this assessment they appear to anticipate the concluding comment of Kripalani and Kulkarni, i.e., that the decadal variability they found in their east Asian study "appears to be just a part of natural climate variations."

More recently, Fleitmann et al. (2004) used high-resolution stable isotope records from three stalagmites in a shallow cave in Southern Oman to develop an annually-resolved record of Indian Ocean monsoon rainfall over the past 780 years. This record revealed that over the last eight decades of the 20th-century, when the earth warmed considerably, Indian Ocean monsoon rainfall declined dramatically, again in stark contrast to what has historically been predicted by most climate models. In addition, the record's other single most substantial decline in monsoon rainfall coincided with a major temperature spike identified by Loehle (2004) in the temperature records of Keigwin (1996) and Holmgren et al. (1999, 2001) that began sometime in the early 1400s. This abrupt warming, which has also been identified by McIntyre and McKitrick (2003), pushed temperatures above the peak warmth of the 20th century before they fell back to pre-spike levels in the mid-1500s, a rise-and-fall temperature trend that produced just the opposite fall-and-rise trend in the monsoon rainfall record of Fleitmann et al. These real-world observations thus provide strong double-barreled evidence that global temperature variations elicit just the opposite variations in Indian Ocean monsoon rainfall than what has historically been predicted by global climate models.

In another recent study, Bingyi (2005) analyzed 43 years (1958-2000) of NCEP-NCAR reanalysis data and station observations (including sea level pressure, geopotential heights, air temperatures and zonal winds at each standard level from 1000 hPa to 200 hPa), looking for possible relationships between tropospheric temperature and the strength of the Indian summer monsoon circulation. This work indicated that the monsoonal circulation "underwent two weakening processes in recent decades." The first occurred in the mid-1960s and the second in the late 1970s, the latter of which, in Bingyi's words, "may be attributed to significant tropospheric warming over the tropical area from the Indian Ocean to the western Pacific," which "was related with the global warming," again in contradiction of climate model predictions.

Last of all, when the 2004 summer monsoon season of India experienced a 13% deficit that was not predicted by either empirical or dynamical models used in making rainfall forecasts Gadgil et al. (2005) decided to perform an historical analysis of the models' skills over the period 1932 to 2004. In doing so, they found that despite numerous model changes and an ever-improving understanding of monsoon variability, Indian monsoon model forecast skill had not improved since 1932. Large differences were often observed when comparing monsoon rainfall measurements with empirical model predictions; and the models often failed to correctly predict even the sign of the precipitation anomaly.

Dynamical models, however, fared even worse. In comparing observed versus predicted monsoon rainfall from 20 "state-of-the-art" atmospheric general circulation models and one supposedly superior coupled atmosphere-ocean model, Gadgil et al. report that none were able "to simulate correctly the interannual variation of the summer monsoon rainfall over the Indian region." And like the empirical models, they frequently failed to simulate not only the magnitude, but also the sign of the real-world rainfall anomalies.

In light of these many amazing findings, and in spite of the billions of dollars that have been spent on developing and improving climate models over the past several decades, taxpayers have achieved essentially no return on their investment in terms of the models' ability to correctly simulate some of the largest and most important of earth's atmospheric phenomena, i.e., its monsoonal circulations. And for those who think that all we need is a finer resolution model to solve the problem, think again. There has been one recent study of the Indian monsoon using a high-resolution GCM (Brankovic and Molteni, 2004), and as Gadgil et al. note, that model also proved to be "not realistic."

Bingyi, W. 2005. Weakening of Indian summer monsoon in recent decades. Advances in Atmospheric Sciences 22: 21-29.

Brankovic, C. and Molteni, F. 2004. Seasonal climate and variability of the ECMWF ERA-40 model. Climate Dynamics 22: 139-155.

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

Chase, T.N., Knaff, J.A., Pielke Sr., R.A. and Kalnay, E. 2003. Changes in global monsoon circulations since 1950. Natural Hazards 29: 229-254.

Fleitmann, D., Burns, S.J., Neff, U., Mudelsee, M., Mangini, A. and Matter, A. 2004. Palaeoclimatic interpretation of high-resolution oxygen isotope profiles derived from annually laminated speleothems from Southern Oman. Quaternary Science Reviews 23: 935-945.

Gadgil, S., Rajeevan, M. and Nanjundiah, R. 2005. Monsoon prediction - Why yet another failure? Current Science 88: 1389-1400.

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.

Holmgren, K., Karlen, W., Lauritzen, S.E., Lee-Thorp, J.A., Partridge, T.C., Piketh, S., Repinski, P., Stevenson, C., Svanered, O. and Tyson, P.D. 1999. A 3000-year high-resolution stalagmite-based record of paleoclimate for northeastern South Africa. The Holocene 9: 295-309.

Holmgren, K., Tyson, P.D., Moberg, A. and Svanered, O. 2001. A preliminary 3000-year regional temperature reconstruction for South Africa. South African Journal of Science 99: 49-51.

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.

Keigwin, L.D. 1996. The Little Ice Age and Medieval Warm Period in the Sargasso Sea. Science 274: 1504-1508.

Kripalani, R.H. and Kulkarni, A. 2001. Monsoon rainfall variations and teleconnections over south and east Asia. International Journal of Climatology 21: 603-616.

Kripalani, R.H., Kulkarni, A., Sabade, S.S. and Khandekar, M.L. 2003. Indian monsoon variability in a global warming scenario. Natural Hazards 29: 189-206.

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.

Loehle, C. 2004. Climate change: detection and attribution of trends from long-term geologic data. Ecological Modelling 171: 433-450.

McIntyre, S. and McKitrick, R. 2003. Corrections to the Mann et al. (1998) proxy data base and Northern Hemispheric average temperature series. Energy and Environment 14: 751-771.

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.

Overpeck, J. and Webb, R. 2000. Nonglacial rapid climate events: Past and future. Proceedings of the National Academy of Sciences USA 97: 1335-1338.

Singh, O.P. 2001. Long term trends in the frequency of monsoonal cyclonic disturbances over the north Indian ocean. Mausam 52: 655-658.

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.

Last updated 12 July 2006