Week Two Climate Change Course Pt2

(That last post got too glitchy for me to continue with, the cursor kept jumping to different paragraphs to the one I was trying to write in. Apologies for any lack of clarity this may have caused)

Pt2 Recent Climate Change, over the last two million years focused on evidence of predictable and unpredictable variations in the natural factors that have an impact on climate change. Long scale factors tend to be more predictable such as the movement of the Earth around the Sun. Eccentricity (circular or elliptical orbit), obliquity (axis tilt) and precession (axis wobble) can all influence variations in climate. Unpredictable elements concern the climate systems discussed in week one, to do with long term weather/seasonal variations.

What evidence is there? Proxy records such as tree rings or ice cores. Each year a tree’s rings reflect how much photosynthesis occurred. Sunny= wide ring; gloomy= narrow ring. How to trust this is case and not other environmental factors? (ie disease, neighboring trees dying so more resources available) Cross dating, looking for similar patterns in surrounding trees (quantitative) and check old wood too.

Aside from solar variability volcanoes are a main unpredictable natural factor as they cause short term cooling through blocking out solar radiation, by throwing aerosols (particles) high in the atmosphere that block and reflect radiation back into space.

It is difficult to use all this evidence from last 100-150 years to explain why are we heating up as much as we are. Infamous hockey stick graph mentioned.The big new player on the block is the amount of CO2 in the atmosphere.

Following on from this six questions were posed, with interesting links to further reading.  Next blog please…

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