Google for: ipcc "beyond 2100"

Duncan,

The farther you look into the future, the greater the uncertainty of your predictions. How to predict future changes that far in advance for greenhouse gas emissions (to mention a major variable involved), which depend on all sorts of changes, including changes in the world economy, technological changes, political changes, population changes?

How much confidence would you place on ANY climate projections made many decades in advance?

Mariza

Thanks Mariza and Harry. I absolutely agree with your scepticism in the accuracy of climate projections many decades out - especially when we factor in those damn unpredictable humans. But when I plant an oak or a pine seedling in a native forest in Scotland I am making an assumption that the environmental conditions will remain suitable for 300 years or more. Growing a big old tree is an investment that really does take that long - and pretty much all the choices have to be made right at the beginning (genotype+growing location) when our knowledge of the future is at its poorest. So even though knowing what conditions will be that far out is next to impossible, we still have to make those decisions - or else leave our descendants a world without any big old trees. It's a tricky problem!

For Your amusement, you can look up the temperatures for the various

Geologic Time periods, and make a list. The info is on the Internet and is just a Google search away ( well actually about 20 Google searches away ).

You will notice a pattern in temperatures where the 11 C to 15 C current

range of temperature in the Holocene is not the norm. The Norm is

more often far warmer than now, but it can also have far colder spells too.

Sea levels also effect temperatures. If sea levels are Low, then the land is elevated,

so the temperatures are cooler. if sea levels rise, then the land is lower,

and temperatures rise.

10,000 to 8,000 years ago the sea levels rose about 400 feet ( 120 meters ), so

the land temperature at all elevations will and did rise, and the Mountain glaciers

are all melting. The more melting, the more the sea levels rise, the warmer it

gets, because the land is effectively lower. it just takes a very long time to

realize the the results of the small temperature increase ( about 0.8 C for 400 foot

sea level rise ).

When you add in excess CO2, you get more temperature rise of about 0.7 to 0.8 C

so when you add the two together and exceed the 1.5 C thresh hold, then

you get permafrost melting, and the release of methane, which is already happening.

The temperature will reach an upper stable limit somewhere between 16 C,

and 22 C. That upper temperature depends upon, how many forests we can regrow, If we can curb our carbon appetite, if we can capture a large percent of the

methane, and if and when there is a dramatic reduction in Human Population.

The uncertainty in how much the temperature will rise and which will be the

most dramatic causes of the rise.

I have come to the conclusion that it will rise, it is unstoppable, and we had better find some methods to live with it, or we can go extinct. You can not stop something that has about a 15,000 year head start on us.

Dear Duncan,

There are estimates that the average temperatures might be rising as much as 4-5 Celsius degree above their level at the start of the industrial age already by 2100:

http://www.e-ir.info/2013/03/06/no-need-for-despair-yet/

I would though suggest that you consider that we might be able to stabilize global warming to a more manageable level of around 2-3 celcius degree by 2100 when you are planting a tree. If we are not able to do that, the lack of any big old trees would be one of the least problems our descendants would have. Considering climate change planting of deciduous trees is anyway better than conifers, as the first ones have a higher albedo (the percentage of solar radiation they reflect).