CO2 or Ocean Cycles?
By Ed Caryl
We are all aware (or should be) of the warming that took place from the 1970’s to the 1990’s. The calamitologists are firmly convinced that this rise in temperature was due to rising CO2 in the same period. The lukewarmists think it was a combination of factors that perhaps contain some warming due to CO2. Then there is another group who think it was all due to the sun or ocean cycles.
This article will compare an ocean cycle, the Atlantic Multi-decadel Oscillation (AMO), and CO2 as temperature drivers over the last 133 years, since 1880. The annual temperature data is from GISS. The plots are scatter diagrams with temperature on the vertical axis and AMO index or CO2 atmospheric concentration on the horizontal axis.
Figures 1a and b are XY plots of temperature vs. AMO (1a) and temperature vs. CO2 (1b).
The period of 1880 to 1910 was a period of cooling. Unless CO2 was driving that cooling, it seems clear that ocean cycles (or some third forcing, such as solar) were responsible.
Figures 2a and b are XY plots of temperature vs. AMO (2a) and temperature vs. CO2 (2b).
The period from 1911 to 1936 was one of warming, on a similar scale to the recent warming. The amount of CO2 increase has been thought not to be responsible for the warming, and attributed to ocean cycles. Climate sensitivity is easy to calculate from the slope of the trend lines in the temperature versus CO2 plots. Simply multiply the “x” value by the minimum CO2 concentration. If the warming in this period was totally due to CO2, the associated climate sensitivity would be 8.3°C for CO2 doubling from 300 ppm, a value that all will agree is much too large. Again, CO2 isn’t providing the warming.
Figures 3a is a plot of temperature vs AMO and 3b a polot of temperature vs CO2.
Figure 3c below is a zoom in on 1937 to 1950, the near vertical line at the left in figure 3b where CO2 actually reversed slightly for a time:
This was a period of cooling, and it is obvious that CO2 had nothing to do with it. Climate sensitivity would have been a negative 0.465°C for CO2 doubling from 310 ppm. During the cooling 1937 to 1950 period, sensitivity would have to have been an astounding negative 82°C for CO2 doubling. Again, ocean cycles or some other forcing were responsible.
Figures 4a and b are XY plots of temperature vs AMO (4a) and temperature vs. CO2 (4b).
The years from 1970 to 2000 were warming years as can be seen on both plots. Note the R2 values for both plots. Was the warming due to CO2? Or was it ocean cycles? The R2 values are voting for ocean cycles, but it isn’t definitive. Remember that Salby and myself have made cases for temperature driving CO2, and not the other way around. The slope of the CO2 trend in this period (climate sensitivity) is 3.64°C for CO2 doubling. This is the only time period where the putative climate sensitivity is reasonable, and close to the theoretical IPCC approved number.
Figures 5a and b are XY plots of temperature vs. AMO (5a) and temperature vs. CO2 (5b).
Above is the recent past; the pause period. Not much is happening. The warming is so slight, that the computed climate sensitivity is 0.33°C for CO2 doubling from 370 ppm. The R2 value for CO2 is so low that it should be clear that something else besides CO2 is in charge. The slope on this AMO plot is positive, as it has been for all of the AMO vs temperature plots, but the points are clustered tightly and the R2 value is only 0.19.
In the 133 years since 1880, all the “CO2 is causing catastrophe” furor is based on one 30 year period in that long span. The remaining 103 years, where CO2 was obviously having no effect, are ignored, …are unexplained. Is this justified? Shouldn’t some effort be made to determine what has really happened? If CO2 is the driver of warming periods, and ocean cycles are driving cooling periods, then climate sensitivity was 8.3°C in the early 20th Century, 3.64°C in the late 20th Century, and 0.33°C now. If CO2 is assumed responsible for half the warming, as the IPCC suggests, and other greenhouse gases are responsible for the rest, the numbers then are: 4.15°C for the early 20th Century, 1.82°C for the late 20th Century, and 0.165°C for the last decade. This may be another indication that climate sensitivity has hit a low limit.
The numbers for CO2 become even lower if changes in solar radiation, solar magnetic effects, cosmic rays, aerosols, volcanic sulfate, soot, dust, water vapor, and changing cloud cover are thrown into the forcing mix. The problem is lack of data. We have good data from satellites only for the last 34 years for temperature, and less than that for many of these other factors. On this paucity of data we are betting our economic future on all kinds of ill-thought out “renewable solutions” that in the long run we will regret.