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Saturday, August 15, 2015

Obviously - what? Bob Tisdale on global mean surface temperature trends

Sou | 7:58 AM Go to the first of 7 comments. Add a comment

"Obviously, Cowtan and Honeycutt are overlooking something very important. Their graph shows that it took well over a century for global surface temperatures to reach the 1.0 deg C halfway point. Many newcomers will look at the graph and wonder what all of the hubbub is about."

Oh my! Those words were actually written with serious intent. Can you believe it? That's from the keyboard of Bob Tisdale (archived here). He's one of the resident pseudo-scientists at Anthony Watts' climate science denial blog, WUWT. His forte is conspiracy theories, not scientific research.

Let's see what will happen if surface temperatures keep going up at different rates.

First of all, look at what happens using Bob Tisdale's odd "science". Below is a chart showing projected surface temperature, assuming a continuation of a linear trend from three periods:

Data source for actuals: UK Met Office Hadley Centre

It doesn't look good, does it.

Bob pointed out to a recent article by Rob Honeycutt at, which demonstrated that it's quite likely that this year we'll hit the 1°C barrier. The chart used a baseline of 1850 to 1899, as representing the pre-industrial period. I can't use the actual pre-industrial temperatures for reasons that should be obvious (the global records don't go back that far, except for BEST, and that's iffy for the earliest times).  Still, 1850 to 1899 is close enough.

The periods I've chosen to project from are:
  • 1899 to 2015, the least steep
  • 1950 to 2015
  • 1970 to 2015, the steepest

So, even taking a conservatively realistic period - the most recent one, a linear projection gets us to breaking the 2°C barrier in 2080, well before the end of this century. Some (young) HotWhopper readers would still be hale and hearty at that time, if a bit hot.

It could get much worse

Now if we continue with business as usual, if we keep on adding more and more CO2 to the air, it will get a lot hotter than that. Here is a projection from the most recent IPCC report, AR5, with temperatures reaching anything from 2.5°C to around 5.5°C above 1986-2005 by the end of this century, under the highest emission pathway (RCP8.5). That's about 3°C to 6°C above pre-industrial:

Figure 12.5: Time series of global annual mean surface air temperature anomalies (relative to 1986–2005) from CMIP5 concentration-driven experiments. Projections are shown for each RCP for the multi model mean (solid lines) and the 5–95% range (±1.64 standard deviation) across the distribution of individual models (shading). Discontinuities at 2100 are due to different numbers of models performing the extension runs beyond the 21st century and have no physical meaning. Only one ensemble member is used from each model and numbers in the figure indicate the number of different models contributing to the different time periods. No ranges are given for the RCP6.0 projections beyond 2100 as only two models are available. Source: IPCC

Now look at how this compares with the global mean surface temperature since civilisation, from Marcott13. It will probably lie somewhere in the orange-red range - way, way above anything humans have experienced:

Data sources: Marcott13 and GISTemp

Minimise global warming - Tisdale style

Bob went to great lengths to minimise global warming. I don't think he will succeed. If he had any influence, which he doesn't, he would increase the rate of warming, not decrease it, because it's fairly clear that he doesn't want anyone to do anything to slow it. Bob put up some spaghetti charts of model runs, with no idea of what he was doing. Then at one point he wrote:
Based on the linear trend of the GISS LOTI reconstruction, global surface temperatures have only risen 0.9 deg C since 1880. See Figure 5. It’ll be a while longer (maybe a decade, based on the linear trend from 1880 to 2014) until we reach the halfway mark of the 2 deg C threshold.

Why would he take a linear trend from 1880, you ask? Good question and one for which I have not the faintest idea. It does indicate that he doesn't have the first clue about climate change and how it's the amount of CO2 in the air that determines warming. (Bob's a greenhouse effect denier by the way.) The trend has been increasing as CO2 accumulates. It's now much greater than the trend from 1880.

Bob closes with this vacuous comment, showing his conspiratorial tendencies (Criteria 1 and 5: Nefarious Intent and Something Must be Wrong):
Using pre-industrial times as the bases for anomalies helps to illustrate something very important to persons new to global warming: climate models do a poor job of simulating past global warming. Why then should those newcomers believe the political-agenda-financed climate-model predictions of future global warming that are based on speculations about yet-to-come emissions of greenhouse gases?

From the WUWT comments

wickedwenchfan thinks that Venus is cold and has no greenhouse effect!
August 14, 2015 at 4:55 am
Venus. 1000millibars= 66C
More than 3400 times the pre industrial concentration on Earth yet closer to the sun. No global warming. No greenhouse effect. None. Zero. Nada. Zilch.

commieBob has his tipping points confused, I'd say. There are realistic tipping points in our near future (or recent past), but they relate more to ice and sea level, not surface temperature:
August 14, 2015 at 5:09 am
We used to hear about a “tipping point”. If that temperature were exceeded then non-linear positive feedback would cause the temperature to soar to catastrophic levels.
Have the alarmists given up on the tipping point?

buckwheaton is motivated to deny science for political reasons, so he conjures up a conspiracy. It probably doesn't register with him that his fears are more likely to be realised if we don't act to curb global warming soon:
August 14, 2015 at 5:22 am
I am awaiting sound research showing the optimum climate for our present biosphere. But most “research” is really an attempt to secure the optimum level of government intrusion in our lives.
It is no surprise that almost every demand made by advocates of global warming converges on bigger government, higher taxes, less freedom and more restrictions on how we choose to live our lives. That tells me all I need to know about this massive fraud.

dp seems to think someone is surprised that it's warming. Of course plenty of people would be very surprised if it happened by magic, as he suggests:
August 14, 2015 at 5:39 am
Temperature rise since the late 1800’s is how we know the Little Ice Age ended then. For a little ice age to end there necessarily needs to be warming. That happened – why is this a surprise? Glaciers that advanced during the LIA are now receding. That is happening. Why is *this* a surprise?

J needs to look at the last chart up above. Then he might see things differently. He'd not be able to discern his medieval or Roman warm period, compared to where we're heading.
August 14, 2015 at 6:17 amI choose the medieval or Roman warm period as my reference period for anomalies.
Now things don’t look so bad ! 

MarkW is one of the self-deluded deniers. A regular at WUWT and a wilful ignorant.
August 14, 2015 at 9:48 am
There’s still the fact that the so called 2.0C limit was just made up, there never was any basis for it. Regardless, the roman and Minoan warm periods were apparently hellish, because they both broke that limit. 

References and further reading

The 1C Milestone - by Rob Honeycutt at

Qin, Dahe, Gian-Kasper Plattner, M. Tignor, Simon K. Allen, Judith Boschung, Alexander Nauels, Yu Xia, Vincent Bex, and Pauline M. Midgley. Climate change 2013: The physical science basis. Edited by Thomas Stocker. Cambridge, UK, and New York: Cambridge University Press, 2014. (available here)

Marcott, Shaun A., Jeremy D. Shakun, Peter U. Clark, and Alan C. Mix. "A reconstruction of regional and global temperature for the past 11,300 years." science 339, no. 6124 (2013): 1198-1201. DOI: 10.1126/science.1228026 (pdf here)

Venus Express - European Space Agency website all about Venus


  1. To think there are those so utterly, brazenly, and idiotically convinced that Venus is cold, all to bolster their all-consuming cognitive dissonance, about a theory that they are so wrong about, they're not even wrong.

    1. Well, in his "defense" he "equates" the Earth situation and the Venus situation by taking the surface of the Earth and "equating" it to the level in Venus' atmosphere which is at 1000 millibars 49.5 km up. That way it all makes "sense".

      Isn't science all about equating things?

  2. Pointing to the fact, that the 1°C halfway point was reached in more then one century, using a graph showing the imminent 1 °C point to be reached in less than 3 decades from that point, and still babbling about a linear trend is simply priceless. Obviously Tisdale lacks the capacity to reflect whats he's talking about.

  3. Tisdale and WUWTians are proof comprehensive that stupid people should not be allowed access to computers or sharp instruments.

    1. This comment has been removed by the author.

  4. It matters not that Tisdale, Ball et al make endless spectacles of themselves because to those inside the bubble they will always be the giants of science.

    Anthony needs a high post turnover rate and his adoring commenters are pathetically undemanding. Never mind the rigour feel the thickness.

    As I pointed out yesterday, Dr Judith Curry linked to a denialist's appallingly written and vastly unfunny satire in the Daily Caller. Standards aren't worth a tinker's cuss in the Denianation


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