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OT: Moorabal/Lal Lal wind farm 10-Jun-2009 At 9:41:51 PM R James

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On 10/06/2009 wombly wrote:
>Question for tony/rjames:
>
>if you have studied:
>
>> long term data (2,000 years up to 450,000 years) there's no evidence
>that our current climate trends
>>are unusual. A lot of focus is put on the last 160 years for no good
>reason, other than that's the span
>>of direct temperature measurement (sometimes called "recorded history".
>What specifically is
>>unusual about our current climate that hasn't happened before many times?
>
>you'll know that there's been some pretty big climate shifts during this
>period on a 100,000 year cycle -
>it's the dominant story over the last million years or so, and has been
>found in so many places (ocean
>temperatures, ice sheet changes, vegetation shifts, river lake expansions
>and contractions, the list
>goes on). Milankovich (i.e. orbital) forcing on this timescale is pretty
>piddly when compared to these
>changes - the main periodicity for those cycles is 40,000 years and 21,000
>years.

Yes, I'm very aware of these cycles. In fact, if history repeats itself as it has for the past five cycles, we're due for a big temperature drop of about 8 degC. This could start any time, but will take a few thousand years to really make much impact

Changes in other
>factors, such as albedo (i.e snow and ice reflecting more sunlight), or
>ocean currents are important
>part of the story, but none of these are enough, even in concert. The
>answer is that you can only
>explain these shifts by the effect of CO2 and other greenhouse gases.

A big NO!!! to that. Why, of all things, would you blame CO2? Sure it's one of hundreds of possibilities. Why not blame changes in solar activity, cloud formation, ocean currents, cosmic radiation, gravitational changes, humidity changes (most significant greenhouse gas), underwater volcanoes (about 5,000 of them), tectonic plate shifts (which effects ocean currents), random variation, - the list goes on and on.

I express surprise at CO2 because it's the most studied possible cause at a cost of billions of dollars, and still has no real data to back it up.

As for high CO2 levels, there is a lot of mixed research on past levels. Ice cores indicate that past levels were lower. However, there is much concern that ice core samples underestimate levels from the past. There's really no way to know for sure. Other sources indicate that levels have been much higher in the past. I have no idea which is correct. Personally, I expect CO2 levels to start to level out in the next few years, particularly of global cooling continues (which it may not do - further warming wouldn't be unusual, though, except for the IPCC, cooling seems to be the expectation from many scientists).