Watt about Bob and William

Although I’ve somewhat changed the focus of this blog, there is a post over at Watts Up With That (WUWT) that has made me decide to have another Watt about … post. It’s a post by Bob Tisdale and is essentially a complaint about Real Climate co-founder, William Connolley. It appears to relate to Bob Tisdale’s announcement that he was retiring from climate change blogging. Roger Pielke Sr responded to this news with a comment that ended with

Your work really should be funded by the NSF or other such grant awarding organizations. I suggest giving that some thought!

If you’ve read some of my earlier posts, you’ll know that I’ve been rather critical of Bob Tisdale’s ideas with regards to global warming, so I read Roger Snr’s comment with some amazement. I, however, really did laugh-out-loud at William Connolley’s response

ROTFL. That made my day.

Bob, however, was clearly not impressed – hence the recent WUWT post. The post itself is not that bad (in terms of Ad hominens at least), but the comments are amazingly vitriolic and probably illustrate why I decided to change the focus of this blog. I’m somewhat impressed that William Connolley decided to engage there. I don’t think I would have been able to do so, and even if I did have the gumption to engage there, I would probably regard it as pointless – although I suspect William feels the same, despite his attempts to engage.

I don’t really want this post to be about the vitriolic attacks on William Connolley (as objectionable as they are), so thought I would try to illustrate why suggesting that Bob’s work should be funded by the NSF is laughable. Bob’s basic idea is that global warming can be largely explained by ENSO cycles (El Niño and La Niña events). To be fair, Bob’s recent explanation of El Niño and La Niña events was pretty good. However, as pointed out by Sou, it would be nice if he gave some credit to others, as it seems clear that he did not develop our understanding of ENSO cycles alone (or contributed at all, for that matter).

The issue with Bob’s basic idea is probably best illustrated in his post discussing his disagreement with Skeptical Science. Bob says

And how and why the RSS lower troposphere temperature anomalies for the latitudes of 20N-90N do not cool proportionally during the La Niña event of 1998-01, Figure 2, but they did warm significantly in response to the 1997/98 El Niño, which caused another major portion of the long-term trend.

and then shows the following figure.

credit : Bob Tisdale, WUWT

So, Bob is essentially arguing that because there is a surface temperature rise associated with the El Niño event in 1997/1998, but no corresponding reduction in surface temperature associated with the following La Niña, that global warming is because El Niño events cause warming, while La Niña events do not cause a corresponding amount of cooling.

The problem is that Bob is probably right about his data, but completely wrong in his interpretation. If anything, what he presents is essentially what one would expect in the presence of anthropogenic global warming (AGW). Let me see if I can explain why. I may not get this quite right, but I think the general picture is correct. As usual, happy to be corrected by those who know more than me.

As Bob himself explains, an El Niño event is when the trade winds are such that warm water is spread across the surface of the Pacific. This results in more energy being released into the atmosphere, producing some warming – potentially an increase (globally) of 0.1 – 0.2^oC. The heat content of the land and atmosphere is, however, quite low. This means that if the planet were in temperature equilibrium prior to the El Niño event, this excess energy should be lost in a matter of months. So, why – after the 1997/1998 El Niño event – did the surface temperature not drop back to the previous value? It’s because anthropogenic forcings meant that there was a net energy imbalance and the El Niño event simply acted to drive surface temperatures closer to equilibrium. The temperature didn’t drop back to pre-event values because the El Niño event did not act to drive the temperature above the equilibrium value – which is what one would have typically expected in the absence of AGW.

Why wasn’t there a corresponding cooling during the following La Niña event? During a La Niña, the surface of the Pacific is anomalously cold (or the warm water is forced to the West). One might expect this to somewhat reduce the global surface temperature (since there is more cold water on the surface of the Pacific) but I don’t think one would expect a La Niña to suck heat out of the land and atmosphere. Given the reduced surface temperature, it will emit less energy and, hence, effectively absorb more of the incident solar flux (presumably replacing some of the energy lost during the previous El Niño event).

So, in the absence of AGW one would – I think – expect El Niño events to be associated with an increase in global surface temperatures that decay quite quickly (months) back to the pre-event value, while La Niña events would be associated with small reductions in surface temperatures and the recovery of the ocean energy lost during the El Niño event. On average, one would expect the global surface temperatures to be roughly constant (i.e., ENSO cycles should not, by themselves, produce a long-term surface warming trend). That El Niño events are associated with step increases in surface temperatures indicates that the pre-event surface temperature is below equilibrium (due to anthropogenic forcings) and the El Niño event is simply a mechanism for rapidly driving surface temperatures towards equilibrium.

So, I have no doubt that this post is not going to, in any way, make Bob Tisdale consider that he may be mis-interpreting the influence ENSO cycles. I’m not the first – nor the most knowledgeable – to try and explain why he’s wrong. I also may not have explained this as well as I might have, so clarifications are welcome. However, given that Bob Tisdale appears to not understand the basics of energy conservation, laughing at Roger Pielke Sr’s suggestion that his research should be funded by the NSF does appear to be the only sensible response. I have no idea whether or not William Connolley can grasp a complex subject (as suggested by Bob Tisdale – I suspect that he is more than capable of doing so), but it does seem clear that Bob Tisdale is incapable of understanding something quite simple.