Saturday, May 7, 2011
Playing with Charts
I am still just messing around trying to get clearer charts. This one though is kinda interesting. This is the RSS surface temperature. The blue line is global (82.5 to -70), red is the northern hemisphere (82.5 to 0) and the yellow is southern hemisphere (0 to -70). All with linear regressions extending to 2097. Since the data starts in 1979, I took the rough middle of the data, 1995, and ran new trends for the second half of the data series. This adds the darker purple line for the northern hemisphere, green for the global and lighter purple for the southern hemisphere. All the data are temperature anomalies with the y axis being degrees C.
All this chart shows is that the trend of the rise in temperature has decreased since 1979, based on this data. Climate changes so that is not very special. What is special is explaining why it changes. What is even more special is explaining why it doesn't change the way people explain it should change. I am not good enough to do either of those. I can look at things and see where they don't add up.
This chart is using GISStemp data. I plotted 1950 to 1979 with trend in blue, 1979 to 1995 with trend in red and 1995 to 2010 in yellow with trend. The trends extend to 2100. Plotted this way the temperature trend is rising and accelerating. This is not an apples to apples plot to compare with the RSS, so here is another chart for better comparison.
Since the RSS data starts in 1979, I can't do an exact chart to compare to the GISStemp 1950 chart. So I did 1979 to 1995 with trend in blue and 1995 to present with trend in red. !998 was a big temperature year, so I added a 2000 to present in yellow to give a little idea how much it impacted things. Plotted this way, the chart shows that the rising temperature trend is accelerating. Discounting the super El Nino year of 1998, it is still accelerating only less.
Using the GISStemp plot and a little imagination, you could see a few more future periods producing the estimated green house warming that could be roughly 3.3 degrees. Using the RSS plot and the same imagination, the 2100 temperature would be less than 2 degrees warmer. GISStemp and RSS are the warmer of the temperature averages in their categories.
Adding a little more realism to that imagination, you would see that all trends are not created equally. Then the GISStemp 3.3 degree rise would look like a maximum temperature rise.
There are a few of the climate scientists that think the IPCC upper end of the range, 4.3 degrees, is a bit high. One, James Annan, thinks that the IPCC might consider 4.0 degrees as the realistic maximum. While I don't count, I agree that 4 degrees appears to be a realistic maximum, with the range 1.3 to 2.1 as the highest probability. I decided on that range mainly due to the satellite data with an estimation that the nearly flat 2000 trend will continue another 10 to 15 years. For whatever reason, global temperature trends as data is complied, tends to have 25 to 30 year trends. These up trends tend to have a steeper slope than the down trends. There is also the possibility of neutral trends. CO2 warming may amplify the up slopes and tend to neutralize the down slopes, but it is unlikely CO2 will eliminate the apparently natural trends. Based on the 1979 to present which includes the super El Nino, the amplification would appear to be rather mild compared to the predictions made in the 1980's and 1990's. The average of the slopes of the 1995-present and 2000-present linear regressions in the last RSS chart should be close to what is expected.
NOTE: The zero of the RSS plot is higher than the zero of the GISStemp plot. That is why my minimum, 1.3 degrees is higher that the RSS chart would indicate.
So without denying anything or cherry picking anything (I guess they could argue about the 2000-present, but trying to filter out the super El Nino, I feel is reasonable), the degree of CO2 warming appears to fall in the lower half of the IPCC range.
There is one thing that everyone should be aware of. Going back to the first chart, the northern hemisphere warming is greater than the southern hemisphere warming. A good part of that is due to the difference in land mass, but a good deal is also due to the land use of that land mass. Why not focus more attention were it is obviously needed?
Update: As an after thought, I decided to add this revised chart of the last RSS chart with the 1979 to 1995 trend and the 1995 to present trend. In this one I added a plot for 5.71ln(CO2/CO2preindustrial)-1. The -1 is to offset the 1979 start to match the zero of the other chart. For pre-industrial CO2 I used 280 ppm, the 1979 CO2 I estimated at 332ppm with 1.9 per year increase to yield 394 ppm in 2011. The logarithmic regression openoffice decided on is in the upper left corner of the chart. This plot for CO2 increase happens to intersect 2097 at 3.5 C which is pretty close to the IPCC estimate, depending on your starting point. I added this more to show that a simple linear regression is not bad for estimating the temperature by the end of the century.
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