If I may chip in, again…
Girma, your intuition that the trend for 2000-2020 is unlikely to be as high as 0.2 C/decade is sound. I agree it is unlikely to be that high.
It’s just that giving a formal mathematical basis for that likelihood is not particularly simple.
For myself, I’ve suggested that 2005-2025 is likely to be below 0.2; and specifically somewhere from 0.15 to 0.2, but that’s a quick guess not a calculation, based on rough consideration of decadal scale variability/
As for the trend extending the 15 years Leake was looking at from 1997; I’ve hacked my spreadsheet to look for parallel cases in the past, where a low 15 year trend has developed into a high 20 year trend.
The biggest such jump is back mid-century.
Trend 1942-1957: -0.185
Trend 1942-1962: -0.026 http://bit.ly/ycGDSO
Trend increases by 0.159; except it’s from really negative to slightly negative, rather than being from flat to strongly positive.
Another slightly smaller increase (by 0.113) on positive trends is this one
Trend 1962-1977: -0.027
Trend 1962-1982: 0.087 http://bit.ly/zIiyKU
However, one thing I think — and on this I certainly agree with Chief Hydrologist — just looking at trends alone isn’t all that useful. Knowing the physical causes for things is a better basis for looking at what may happen.
Chief cites interesting work by Swanson and Tsonis, which proposes a physical basis for a lull extending out to roughly 2020. Furthermore, their proposal also highlights the two “jumps” I list above. This all constitutes a physical reason for suspecting the 20 year trend won’t be up to 0.2. They do predict the same underlying non-periodic warming trend will continue to be the main factor through this century; their model is that the internal variation is greater than the IPCC projection would suggest. This also implies GREATER climate sensitivity, not smaller. You need more sensitivity to get a big response to these internal factors. They make this point explicitly in their work.
Be that as it may, their proposal, if it pans out, would almost certainly result in the IPCC prediction failing over the immediate future out to 2025.
Cheers — Chris