johnfajardohenry wrote:I am repeatedly told here that warming temperatures were predicted and have been observed and so there has been one prediction that came true.
Yes, IF temperatures have actually increased (by 0.8 deg. Or is it 0.65 now?), this would have been a valid prediction that came true. There are so many problems with the way temperature data has been collected and manipulated that it takes a real leap of faith to believe in it. [...]
I've discussed the various problems with the temperature data in various threads here before and will be happy to do so again if anyone wishes. For the moment, I'll just say that I find it completely untrustworthy.
Let's take this one piece at a time.(1) Predictions:
Two early papers containing quantitative predictions of global warming were Broecker et al. 1975
and Hansen et al. 1981
, discussed in detail here
Writing in 1975, Broecker et al. predicted approximately 0.8C of warming from the mid-1970s to the early 2010s, as shown in their Figure 1:
Meanwhile, Hansen et al. predicted approximately 0.5C of warming by the early 2010s, as shown in their Figure 6:
It is worth noting that both papers occurred at the end of a period of 30 years of basically flat temperatures globally. Thus, both Broecker et al. and Hansen et al. were predicting a radical change from current conditions at the time -- they were not merely extrapolating an existing warming trend. (2) Observations:
Here is the actual global temperature trend -- or rather, two completely independent versions of the global temperature trend.
The blue lines show global mean temperature based on measurements at meteorological stations (on land) and from ships (prior to 1979) and satellites (since 1979) for the ocean.
The red lines show global mean temperature measurements since 1979 from a completely different set of satellite instruments (microwave sounders, which measure temperature-dependent emissions of microwave radiation from the lower atmosphere).
In both cases, the thin lines are monthly averages and the thick lines are three-year smoothed trends (using a statistical filter know as LOESS).
Note that the MSU satellite observations lie almost exactly on top of the land & ocean observations. Thus, we have two completely independent sets of data showing basically the exact same warming trends from 1979-present.
This negates John Henry's concern about the reliability of the temperature data. Since there is no connection between the methods or sources used to produce the two data sets, the fact that they show similar trends is very strong evidence for their accuracy. (3) Comparison of Predictions and Observations:
In this figure, I have overlaid the actual, observed temperature data on top of Broecker's predictions from 1975:
It is evident that Broecker's model (green line) slightly over-predicted warming. One issue is that Broecker's model assumed that the earth would respond rapidly to a climate forcing, whereas in reality there are time lags in the climate, such that the effect of an instantaneous warming will be smeared out over a period of decades.
Meanwhile, Hansen's 1981 prediction somewhat under-estimated warming:
Note that recent temperatures have been at or above the top of the range of predicted values in Hansen's paper.
This is, frankly, astonishing. Working at a time when only very sketchy global temperature data were available, and when computers were primitive compared to today's, two separate research groups managed to come up with highly accurate predictions of global warming.
I don't blame John Henry for not knowing about this, since the media have generally done a terrible job of reporting on climate science issues in the US.
But in point of fact, we can say with a high degree of confidence that the earth has warmed since the 1970s, and that the early, path-breaking predictions of Broecker et al. and Hansen et al. have turned out to be remarkably accurate.