Short-term Weather Patterns: They Mean Nothing. - Page 4

Originally Posted by segovius

Are you seriously saying - seriously saying - that this is how you understand what I wrote ?????

Originally Posted by BR

I don't bury my head in the sand when reality doesn't match what I really want to believe.

Originally Posted by MJ1970

If I have misunderstood, then I will apologize. To avoid further confusion I will ask you directly: Do you believe and/or are you saying or implying that the questions I posted are examples of "irrationality, unreason and stupidity?"

Originally Posted by segovius

No..you said I was a denier and I agreed - those are merely examples of things which I 'deny'.

Apologies not needed.

1. Is the earth warming? Yes? No?
2. If yes, then is it warming to a degree or at a rate that threatens humankind? Yes? No?
3. If yes, is there anything we can do about it? Yes? No?

[T]wo studies in this week's Nature1,2 conclude that climate warming is already causing extreme weather events that affect the lives of millions. The research directly links rising greenhouse-gas levels with the growing intensity of rain and snow in the Northern Hemisphere, and the increased risk of flooding in the United Kingdom.....
There is no doubt that humans are altering the climate, but the implications for regional weather are less clear. No computer simulation can conclusively attribute a given snowstorm or flood to global warming. But with a combination of climate models, weather observations and a good dose of probability theory, scientists may be able to determine how climate warming changes the odds. An earlier study3, for example, found that global warming has at least doubled the likelihood of extreme events such as the 2003 European heatwave.....

Given that atmospheric water-holding capacity is expected to increase roughly exponentially with temperatureand that atmospheric water content is increasing in accord with this theoretical expectation6, 7, 8, 9, 10, 11it has been suggested that human-influenced global warming may be partly responsible for increases in heavy precipitation3, 5, 7. Because of the limited availability of daily observations, however, most previous studies have examined only the potential detectability of changes in extreme precipitation through modelmodel comparisons12, 13, 14, 15. Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. These results are based on a comparison of observed and multi-model simulated changes in extreme precipitation over the latter half of the twentieth century analysed with an optimal fingerprinting technique. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming16.

Although the flooding was deemed a wake-up call to the impacts of climate change at the time7, such claims are typically supported only by general thermodynamic arguments that suggest increased extreme precipitation under global warming, but fail8, 9 to account fully for the complex hydrometeorology4, 10 associated with flooding. Here we present a multi-step, physically based probabilistic event attribution framework showing that it is very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000. Using publicly volunteered distributed computing11, 12, we generate several thousand seasonal-forecast-resolution climate model simulations of autumn 2000 weather, both under realistic conditions, and under conditions as they might have been had these greenhouse gas emissions and the resulting large-scale warming never occurred. Results are fed into a precipitation-runoff model that is used to simulate severe daily river runoff events in England and Wales (proxy indicators of flood events). The precise magnitude of the anthropogenic contribution remains uncertain, but in nine out of ten cases our model results indicate that twentieth-century anthropogenic greenhouse gas emissions increased the risk of floods occurring in England and Wales in autumn 2000 by more than 20%, and in two out of three cases by more than 90%.

Human influence on climate has been detected in surface air temperature1, 2, 3, 4, 5, sea level pressure6, free atmospheric temperature7, tropopause height8 and ocean heat content9. Human-induced changes have not, however, previously been detected in precipitation at the global scale10, 11, 12, partly because changes in precipitation in different regions cancel each other out and thereby reduce the strength of the global average signal13, 14, 15, 16, 17, 18, 19. Models suggest that anthropogenic forcing should have caused a small increase in global mean precipitation and a latitudinal redistribution of precipitation, increasing precipitation at high latitudes, decreasing precipitation at sub-tropical latitudes15, 18, 19, and possibly changing the distribution of precipitation within the tropics by shifting the position of the Intertropical Convergence Zone20. Here we compare observed changes in land precipitation during the twentieth century averaged over latitudinal bands with changes simulated by fourteen climate models. We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel.