Study: $45 trillion needed to combat warming

[cosmicalstorm]

What is the worst case respectively the best case scenario for the next few decades provided we basically just continue to do what we do now? (wich is nothing from what I understand)

[Mr. T]

What is the worst case respectively the best case scenario for the next few decades provided we basically just continue to do what we do now? (wich is nothing from what I understand)

Alot depends on what's known as the "climate sensitivity". This basically refers to how much the temperature increases with a doubling of CO2 concentrations in the atmosphere over pre-industrial emissions times. An equivalent doubling is 480 ppmv of CO2 in the atmosphere.

Given a CO2 doubling, the climate is projected to warm anywhere from 1-4.5 degrees celsius according to projected models.


- A 1-2 degree warming could provoke the irreversible collapse of the West Antarctic ice sheet which would raise sea level by 5-6 metres(but this would take several hundred years to occur)
- An IPCC summary shows a Co2 doubling to decrease agricultural yields in specific regions by 10-20% or more. Alot of the worlds food, rice and grain etc. are right now in midlattitude areas/the developing world being grown at or close to there optimal temperature and so a temperature increase will reduce yields
- A 2-4 degreee warming risks provoking the irreversible melting of the Greenland Ice sheet, which would raise sea level by 7 metres (although this would take 1000-5000 years to occur)
- A 1-2 degree warming risks killing most or all of the coral reefs in the world due to the phenomena of coral bleaching, increased ocean acidity (the ocean absorbs CO2 and this has the effect of making it more acidic over time) and the fact that corals need a minimum amount of sunlight to survive which may not be possible with rising sea levels
- In one simulation, a warming of 3-4 degrees celsius over the course of the next century shows the entire Amazon rainforest being replaced by desert by 2080


- Sea level is expected to rise 25-70 cm by 2100
- Among other things, sea level rise will lead to salt-water intrusions in to freshwater bodies reducing the available amount of fresh water
- Expected extinction rates of all species by 2050 are a minimum of 18% and a max expected extinction by 2050 of 35%...OF ALL SPECIES
- Health problems are likely to increase, aside from heat stress, mosquito's and disease organisms tend to bite more when the temperature warms, leading to increases in malaria etc, and diseases are likely to spread poleward as well as the northern climate warms as we're already seeing with the pine-beetle that's devestating forests in the Canadian West
- There's a number of positive feedback loops (such as the thawing of Arctic Permafrost which is going to release even more GHG's in to the atmosphere) that will lead to greater warming through increased GHG's. Once we've warmed the climate enough for this to happen, it will happen regardless of whether we continue as business as usual or if our emissions immediately droppped to zero


I may be missing some things but that's the basic summary of what's now being said will happen. Note that the above is only in regards to a CO2 equivalent doubling, if we keep increasing past that the effects will obviously get worse and worse.

[Admiral Valdemar]

Worst case would be a 30 odd metre rise over the next century, assuming the positive feedbacks kick in like Hansen expects as we surge past his lowered limit of 350 ppm for CO2. We're nearer 400 ppm now and things are moving fast.