Is Global Warming a Northern Hemisphere thing?

An illustration in the IPCC report "Summary for Policymakers" based on the fourth Assessment Report "Climate Change 2007" shows a very interesting pattern.

(I'll need to print the page and scan it in - sorry for the delay.)

Refer to page 4 where there is a diagram of the world showing changes in surface temperatures from 1970 to 2004. There is a clear gradient in the degree of temperature change from the Arctic region with up to +3.5o C (increase) to -1o C (DECREASE!) in areas close to the Antarctic in the southern hemisphere.

Why is this? (If you know, please post a comment.)

It is also interesting that over 90% of the "Observed Data Series" for both physical and biological systems are for the Northern Hemisphere.

So, what about these options?

• There is greater land mass in the northern hemisphere. But doesn't the land heat and cool faster than the sea?
• There have been more temperature readings taken in the northern hemisphere and the southern hemisphere temperature data isn't as complete.
• There is a change in the position of the northern hemisphere relative to the southern hemisphere in relation to the sun in the long term cycle of the Earth's orbit.
• There is more industry in the northern hemisphere and temperature change is localised to a greater extent than global.
• Changes in the Earth's magnetic field has caused some particles (which absorb heat such as water vapour) to concentrate more in areas north of the Equator.
• The scientists obtained temperature increase readings in the northern hemisphere more easily than in the southern hemisphere, so they have concentrated on studying those areas.
• There are more politicians in the northern hemisphere (sorry - I couldn't resist that one!)
• The readings which didn't support the Global Warming theory were filtered out.

Interesting, but the illustration covers only a 34 year period. I did enough science at school to know that climatic trends span much greater time periods than that.

Also, the report talks about "average" surface temperature change. If more readings are taken in the northern hemisphere land masses close to cities, then doesn't that make the "average" data skew towards those areas, and not give a picture of the globe overall? That's what I had thought they meant by "average" temperature change up until I saw this illustration. Now I need to find out what data points they used for this average, and how many readings were taken from each.

Concern - Average means average of the data received, not average in global coverage.

Another noteworthy point is that very few of the "Observed Data Readings" are in countries which the United Nation's Millenium Development Goals aim to assist. Hmmmm - that could be worthy of a blog post all on it's own!

Interesting, but not conclusive. I'll keep reading................