Posted by There really is no excuse for this, from Michael Duffy:
Global warming stopped six years ago. It might start again tomorrow, but from 2002 until now, average global temperatures have remained fairly constant. This is in contrast to the previous period when, as everyone knows, the temperature trend was upwards.
Look at the graph below, showing 8-year trends for each 8-year period in the data. (Graph is from RealClimate.) Notice that the eight year trend is sometimes negative. That’s because an eight year trend can be greatly affected by an unusually warm or cold year or two. But Duffy doesn’t say that warming stopped in the 80s and again in the 90s. Instad he says “the temperature trend was upwards”. Which is only true if you look at trends longer than ten years.
Oh and notice that the current 8-year trend is for strong warming — you have to go to just six years if you want to find a trend that doesn’t show warming.
Duffy is aware of Fawcett and Jones explanation that warming hasn’t stopped:
A good source for this position is the paper Waiting For Global Cooling, published last month by Robert Fawcett and David Jones of the National Climate Centre at the Australian Bureau of Meteorology.
And some blog that’s been going on on this simple point for years now:
The mainstream view is represented by the University of NSW’s Tim Lambert at scienceblogs.com/deltoid
But he doesn’t seem to understand. Look:
It’s worth reflecting on the number of scientists who are certain about what the temperature trend will be in a 100 years, yet in 2001 were unable to predict what would happen in the next six.
I can’t tell you with any accuracy the percentage of heads you will get if you toss a single coin, but I can tell you that you will get close to 50% heads if you toss a thousand coins. I guess Duffy would argue that if I can’t tell you the result of one toss I can’t possibly predict the result of a thousand tosses.
Here’s Michael Ashley’s letter to the Sydney Morning Herald (He’s a Professor of Astrophysics at UNSW):
Michael Duffy (“New climate figures would make a great debate”,
SMH, 3 May 2008) is convinced that there is a global conspiracy to
hush up results from the UK’s Hadley Center that show that the earth
cooled in the six years from 2002.If he had investigated further he would have found that the
Hadley data also show that global warming stopped in six-year or
longer periods beginning in 1941, 1951, 1959, 1969, 1979, and 1987.After each of these periods the earth warmed up to more than
compensate for the drop.The conclusion? Not a global conspiracy of the world’s scientists and
media to protect the orthodoxy against Duffy’s pioneering scepticism,
but simply that six years isn’t long enough to measure the long term
trend.
And here’s Andrew Dessler also explaining it:
There has been a lot of nonsense written about the lack of much if any warming over the last few years. It’s not a new argument — in fact, I blogged about it here — but like an axe-wielding psycho from a cheap horror flick, it just keeps coming back. …
A close look at the plot shows that this situation is not abnormal. In fact, global warming has stopped repeatedly over the last 150 years — meaning that there are many instances when the temperature reached a maximum that took many years to surpass.
The reason is clear. A warming rate of 3 degrees C per century corresponds to an annual average rate of warming of 0.03 degrees C per year. At the same time, interannual variability, such as El Niño events, are of the order of 1 degree C per year. Thus, over short time scales, the slow upward trend can be completely swamped by the large year-to-year variability.
Over the course of several decades, however, the slow warming trend dominates, and you end up with significant warming. Thus, to determine if global warming is occurring, you have to look at time periods of decades, not years.
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