The attribution question is of course a central one in the climate debate.
According to IPCC 90-95% of the temperature rise is due to us humans through GHG and land use since the middle of the last century. At least, that is what is assumed in the climate models. So, the validation of this claim is obviously done by comparing the outcomes of the models and the observations. How are they doing?
Trimming the models through so called "hindcasting" and then releasing them into the future shows a discrepancy on the 95% significance level since about 1998. (If the RSS and UAH satellite data set would have been used, the discrepancy would have been even larger). Looking at the trend - which really is the important thing - the observations do not differ from a zero trend since 1997. The models, however, do an upticking not seen in reality. Why? Two things are possible; the climate sensitivity assumed in the models is too high or the internal (natural) variability of the climate system is not properly accounted for. Either way, the high (human) attribution factor assumed in the models is given less and less support the longer the slow down or Hiatus is prolonged.
Taking a look at one of the important natural climate factors, the AMO, and comparing it to the UAH global temperature data set (satellite launched 1979) gives the graph below:
The Hiatus is clearly seen in both data sets, also the rise since 1979. If this comparison would be used, the anthropogenic attribution factor would be close to zero. (AMO is assumed 100% natural variability).
What is closest to the truth? An honest answer to the attribution question would be "we don´t know". It is not possible IMO to actually untangle the natural variations from the anthropogenic impact just yet. The anthropogenic signal haven´t manifested itself above the natural noise, not to any statistically significant degree anyway. The temperature rise and rate seen in the modern data are not remarkably different from what have been seen in historical data records. (See figure below). We can´t really claim we are "accelerating" things from this.
The question is, are we willing to take the risk or should we curb our GHG emissions? Are there other priorities in the society that should come first? I personally think so
According to IPCC 90-95% of the temperature rise is due to us humans through GHG and land use since the middle of the last century. At least, that is what is assumed in the climate models. So, the validation of this claim is obviously done by comparing the outcomes of the models and the observations. How are they doing?
Taking a look at one of the important natural climate factors, the AMO, and comparing it to the UAH global temperature data set (satellite launched 1979) gives the graph below:
What is closest to the truth? An honest answer to the attribution question would be "we don´t know". It is not possible IMO to actually untangle the natural variations from the anthropogenic impact just yet. The anthropogenic signal haven´t manifested itself above the natural noise, not to any statistically significant degree anyway. The temperature rise and rate seen in the modern data are not remarkably different from what have been seen in historical data records. (See figure below). We can´t really claim we are "accelerating" things from this.
The question is, are we willing to take the risk or should we curb our GHG emissions? Are there other priorities in the society that should come first? I personally think so
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.