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I don't think it is as complicated as they make out.
A number of "political/economical" scenarios have been selected (less than 10? - not sure), and a likelihood assessed for each.
For each one, an assessment is made to changes in GHG, aerosols, numbers of aircraft flights. eg. Anthropogenic GHG emissions will be X per year for the next 100 years etc.
Each model is run with each assessment to give a range of predictions.
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Have you heard about the garbage in garbage out model?
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quote: Have you heard about the garbage in garbage out model?
I looked hard and couldn't find it. I got bored waiting for the experts they might have gone for a long Friday lunch, so I went for the "ready links, cut and paste research or the bible of information on climate change-IPCC to explain this phenemenon." as WIYM would have it. It appears that there is no consensus in the 3rd assessment report on 1910-1940 warming: quote: Natural factors may have contributed to the early century warming.
Most of the discussion in this section has been concerned with evidence relating to a human effect on late 20th century climate. The observed global mean surface temperature record shows two main periods of warming. Some studies detect a solar influence on surface temperature over the first five decades of the century, with perhaps a small additional warming due to increases in greenhouse gases. One study suggests that the early warming could be due to a combination of anthropogenic effects and a highly unusual internal variation. Thus the early century warming could be due to some combination of natural internal variability, changes in solar irradiance and some anthropogenic influence.
At least they're honest. |
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Thanks Steve for the information.
Now can you explain to me if they are not certain for the first period why are they so certain about the second period?
Garbage in- inputs from economists, sociologists, politicians
Garbage out- Climate projections
Clear?
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Well i would have to agree with the principle that WIYM puts forward. What makes the second rise of 0.5dgC from 1980 to 2004 an almost dead cert for CO2(in the 90 to 95% range)and yet when they find a similar rise over a similar time period with no known explanation it doesnt seem to disuade the former view??
I do not beleive this whole thing is a put up job as WINYM but i need to see some consistancy here. If the 1910 to 1940 rise is a quirk - then this must lead to the possibility that the 1980 to 2010 also being one??
Now where does that leave us?
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I did get some information quote: Solar looks likely to have played a substantial part of the warming in the
first half of the century (that and a period of low volcanic emissions
which would show up as a warming after the previous last major volcanic
erruption in the 1890s). There was also a man made component but it is not
possible to understand the global temperature changes during this period
without the inclusion of the sun's changes. From the 1950s however the
long term strength of the suns energy has not changed. The majority of the
warming during this period is due to man made emissions.
I followed up with a question about uncertainty: quote: I am not sure that it is so much uncertainty [in the anthropogenic component]
- in the early part of the last century there was not so large a net anthropogenic
impact.
Which suggests that 1910 was cool due to volcanoes whereas 1980 was already warm. The temperature plot seems to bear this out, but I can't find any corroborating info at the mo. www.metoffice.gov.uk/research/hadleycentre/obsdata/globaltemperature.htmlI can't get to the bottom of the measurements of solar irradiance in the 1910-40 period and how confident they are in the calculations of its effect. Obviously these days calculation of solar forcing is more accurate which is why they rule it out as the major contribution to current warming. I've asked another question on this, but suppose everyone's gone home now. |
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Thanks Steve for the effort. It will great to have further clarifications if possible
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Thanks Steve, interesting. If you do manage to get anything else i would be interested. i am not a scientist so in the end i have to take what the largest group of scientist agree on as the way it is.
In my next life i will certainly choose science over history for my MA. Earth's climate is a truely wonderful thing - Q music dim sun.
Seriously, i have learnt loads in the past few days on this site. I still have a get feel that there are more effects that the science has not yet fathomed, but i think they know that.
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