posted on Sep, 18 2011 @ 06:02 PM
Originally posted by burntheships
reply to post by jimbo999
Look first, speak afterwards.
Of course, here ya go! From the horses mouth itself.
In view of the ongoing public and political debates about climate change, the aim of this
document is to summarise the current scientific evidence on climate change and its
drivers. It lays out clearly where the science is well established, where there is wide
consensus but continuing debate, and where there remains substantial uncertainty
Thanks for the link showing how stupid the deniers are.
What htey have said is that some stuff is certain, some nearly certain, some less so, and about SOME STUFF there is substantial uncertainty.
Firstly is climate change caused by mankind?? Here's ewhat they REALLY say:
There is strong evidence that the warming of the Earth over the last half-century has
been caused largely by human activity, such as the burning of fossil fuels and changes
in land use, including agriculture and deforestation.
Note that - strong evidence" that it is - ther is NO "substantial uncertainty" about that.
Her's what they put in the various categories:
Aspects of climate change on which there is wide agreement:
Measurements show that averaged over the globe, the surface has warmed by about 0.8oC (with an uncertainty of about ±0.2oC) since 1850. This
warming has not been gradual, but has been largely concentrated in two periods, from around 1910 to around 1940 and from around 1975 to around
-the climate is warming
Global-average CO2 concentrations have been observed to increase from levels of around 280 parts per million (ppm) in the mid-19th century to
around 388 ppm by the end of 2009.
-CO2 is increasing
Evidence from ice cores indicates an active role for CO2 in the climate system.
-CO2 helps warming
Changes in atmospheric composition resulting from human activity have enhanced the natural greenhouse effect, causing a positive climate
-man-made gases are increasing the natural increase in temperature
So much for there being "widespread uncertainty" about AGW!
The next section is:
Aspects of climate change where there is a wide consensus but continuing debate and discussion.
Included here is:
Once atmospheric CO2 concentrations are increased, carbon cycle models (which simulate the exchange of carbon between the atmosphere, oceans,
soils and plants) indicate that it would take a very long time for that increased CO2 to disappear;
- So there is still discussion about how long it will take for CO2 to be removed from the atmosphere by "natural" means
In addition to changes in greenhouse gas concentrations, there are a large number of less well characterised contributions to climate forcing,
both natural and humaninduced.
- there are other things helping drive climate change besides the man-made green house gasses eg volcanoes, natural climate change processes,
shorter lived gasses from human activity
The more complex climate models, supported by observations, allow climate sensitivity to be calculated in the presence of processes that amplify
or reduce the size of the climate response.
- there are non-direct processes that may make hte climate more or less sensitive to GHG's - eg water vapour
When only natural climate forcings are put into climate models, the models are incapable of reproducing the size of the observed increase in
global-average surface temperatures over the past 50 years. However, when the models include estimates of forcings resulting from human activity, they
can reproduce the increase.
As with almost any attempts to forecast future conditions, projections of future climate change depend on a number of factors. Future emissions
due to human activity will depend on social, technological and population changes which cannot be known with confidence. The underlying uncertainties
in climate science and the inability to predict precisely the size of future natural climate forcing mechanisms mean that projections must be made
which take into account the range of uncertainties across these different areas.
- forecasts are only forecasts - their accuracy has to be checked with actual data as time goes on, and the models improved accordingly.
On to part 2 next......