This blog will be for the discussion of whatever takes my fancy at any given time. Primarily, that will be Anthropogenic Global Warming/Climate Change
By: Birthmark , 2:34 AM GMT on February 05, 2014
I have one simple question for denialist everywhere – why has the earth been so warm since 1998?
Denialists had been going on and on about the lack of statistically significant warming since 1998. Of course, a lack of statistically significant warming isn't the same as a lack of warming. The earth has warmed since 1998. The question is why has the earth warmed?
Let's begin by looking at the sun.
Figure 1 - Solar cycles 22,23, and 24
We can see in figure 1 above that since the peak of solar cycle 23 solar activity is plunged. The current maximum of solar cycle 24 is, frankly, pathetic. If the sun is a major player in climate, the Earth's temperature should be much cooler than it was at the maximum of solar cycle 24. But that's not the case. The Earth has continued warming.
Perhaps we can learn something from looking at the oceans. Of course, the big player in the oceans is El Niño/La Niña.
Figure 2 - Multivariate ENSO Index
The huge El Niño of 1998 sticks out like a sore thumb. Since that time we've seen much shallower El Niño's and many La Niña's. In fact, there is a slight majority of La Niña was in neutral years since 1998. So this is another factor that should cooled the earth.
Let's take a look at the Pacific Decadal Oscillation (PDO).
Figure 3 - JISAO-PDO index with trendline
We can see that there's been a downward trend in the PDO since 1998. Yet again, here's another factor that should of caused the earth to cool.
But the earth hasn't cooled. Instead, it has warmed since 1998. Figure 4 below shows the UAH temperature data set along with the trend line since 1998.
Figure 4 -UAH temperature data from 1998 to present with trendline
It clearly it clearly has warmed. It should be remembered that UAH is a satellite data set. Therefore, neither the urban heat island effect, nor siting issues are of any relevance.
So I'll go back to the question. I first asked him the question that needs to be answered by denialists: why hasn't the earth cooled? What is keeping the earth so warm since 1998?
EDIT 4/4/2014 -- I replaced Figure 4 with the correct graph for the UAH temperature data set since 1998. I had previously posted the UAH-land data set. (And no one noticed!)
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