Wednesday, 15 April 2015

Extraordinary Claim: The whole world is hotter than it was in 1880 and we know by how much. - continued

The whole basis for the ‘climate change’ scare is based on several assumptions, among them:

1. That the Earth’s surface, its oceans and its atmosphere are warming.

2. That the warming is dangerous.

3. That warming is caused by increases in carbon dioxide and other ‘greenhouse’ gasses.

4. That human activity is the cause of the increases in greenhouse gasses.

5. That humans can’t adapt to a warmer world and so reducing greenhouse gas emissions is the only way to ‘save the planet’.

6. That reducing green gas emissions will actually have the desired effect, that is, will actually lower the Earth’s temperature.

In this and a few future posts, I’ll focus on the first assumption in more detail: How is it possible to measure the Earth’s average temperature both now and in the past to determine whether its warming, cooling or staying the same?

This raises a critical second question: how accurately can something like the Earth’s temperature be measured?

The Claim

As previously reported, the Intergovernmental Panel on Climate Change (IPCC) says in their Fifth Assessment Report “The globally averaged combined land and ocean surface temperature data as calculated by a linear trend, show a warming of 0.85 [0.65 to 1.06] º C over the period 1880-2012.”

When we unpack that statement a bit, it means that the IPCC claims that the temperature of the whole planet and its atmosphere can be measured to sufficient accuracy that we can6 detect a change of 0.85 º C over a period of 132 years. That’s a change of just 0.006 º C per year, or as the IPCC reports, 0.06 º C per decade.

Assessment Report, Climate Change 2013, Working Group I: The Physical Science Basis, Chapter 2, Observations: Surface and Atmosphere. Page 161.

Temperature measurements are calculated (no, they’re not just measured) from a number of sources.  The IPCC uses a blend of three sets of temperature records:

1. HadCRUT4 - Data collected by the Hadley Climate Research Unit for the University of East Anglia in the UK.

2. NCDC MLOST – The Merged Land-Ocean Surface Temperature Analysis data set is produced by the Earth System Research Laboratory, a part of the National Oceanic and Atmospheric Administration which is, in turn, part of the U.S. Department of Commerce.

3. The GISS data  set is produced by the Goddard Institute of Space Sciences, a department within the U.S. National Aeronautics and Space Administration. 

All three claim extraordinary accuracy.

The processing of temperature data is described in mind-bogglingly complex scientific papers. I’ll focus on the HadCRUT data. HadCRUT4 (Morice et al, 2012 *), as is probably not surprising, replaces HadCRUT3 (Brohan et al, 2005 **).



HadCRUT4 vs HadCRUT3

The two sets of data are pretty similar, as the graph above shows, except that the newer HadCRUT4 shows higher recent temperatures starting around 2005. How can past temperatures change? The answer is in how these numbers are calculated.

These number are not just read from a thermometer and written down.  On no! There is a huge amount of processing / fiddling that goes into the temperature records.

In my next post, I’ll review the level of claimed accuracy in the past temperature record and compare it to the result of a little experiment of my own.

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