RE: LeftyLarry
1. .... "ice comes and goes naturally and man adjusts"
2. ..."ice been slowly declining since the end of the ice age"
3. ...."could a volcanic eruption, bring enough cooling to regrow the lost ice and stop the long term patterns of continued loss"
4. "If all the ice melted and the oceans rose , wouldn’t there still be a huge net gain of habitable land overall?"
Whether trolling or not, these are questions/assumption many people have, including the U.S. Secretary of State, who recently suggested that people will just move to accomodate a change climate, that climate has always changed, etc.
What is missing in those perspectives is a sense of scale for time and impacts, along with some basic misunderstandings.
My take on 1-4.
1. As others here have noted here and elswhere, it's one thing for a nomadic society of let's say 7,000 humans to move their tents inland in response to millenial rates of change. Quite another for 7 billion humans with massive infrastructure investments and needs to react to rates of change 10x to 100x faster, thus decadal changes as large as what happend across a 1,000 years in the past.
2. Others here have commented here in more detail. I'll just add that the "natural" trend has been a gradual cooling since the Holocene peak a few thousand years ago. Gradual because that cooling was due primarily to natural, = very slow, shift in orbital cycle. What humans are doing to atmosphere, starting with use of coal as energy source starting ca. 1750, and esp. since 1970 with global increase in fossil fuels, is orders of magnitude more intense and faster than even the most radical climate shifts that led to mass extinctions (90+% of species) in the geologic record.
3. Even another Tambora eruption (which caused the "Year without a summer" in New England in 1816) won't protect us from our radical heating of the Earth. While some climate scientists say the temperature effect is discernible longer than the usually cited 'couple of years', it is temporary nonetheless. A cooling caused by volcanic emissions into the stratosphere, or a synthetic version through geoengineering, also does nothing to reduce ocean acidification. Geoengineering to reduce solar energy also introduces major risk of disrupting monsoon and other weather patterns. "Let's try this, what could go wrong?" Lots.
4. Moving from recently inundated coastlines to newly exposed land formerly under ice caps would bring with it economic and humanitarian destruction of unprecedented scale in the history of human civilization since 4000 B.C.E.. But in addition, just moving the crop belts north isn't going to work. The temperature bands will move north, but the amount of solar radiation for photosynthesis isn't changing, and the glaciated soil types in central Canada, for example, are not the same as Iowa which used to have 10 feet of top soil in places. It's going to be tough enough to feed 10 billion people in 2050. Doing that with degraded ag productivity, which is the consensus projection for global average temperature beyond +1.5-2C (mixed results for lower temp. change) could be impossible.
And don't let anybody fool you with the "CO2 fertilization" smoke screen. Increasing CO2 can indeed increase plant growth under controlled conditions where everything else is supplied at optimum (water, fertility, temperature). Raise CO2 to 450-500ppm in the real world and you won't get any plant growth benefit because those other inputs are not optimized. Major world food crops are near their thermal maximum now. Increased temperatures would/will take them over the top of the curve and onto the declining production side even if water supply wasn't an issue. Moreover, studies find that for the plants that we eat, aka "crops", while they can be grown bigger under higher CO2 with those perfect conditions I talked about above, the density for key nutrients goes down, so a person would have to consume more to get the same amount of nutritional benefit.
Bottom line - climate disruption is going to kill people. Lots of them. The brown and poor people will get hit first, but nobody will escape the consequences of altering the basic life support system of planet Earth. And by the way, we can't go to Mars. Think about how many people on Earth it would take to support a colony of a dozen people living inside canisters on Mars.
So if you love your grandkids (and how could you not) then do everything you can to raise awareness and alarm because this really is a crisis. It is an unnecessary and avoidable crisis, because we already have the technical capability to produce the energy we need without suicidal continuation of fossil fuel addiction. The real issue is one of character, long-term wisdom vs. short sighted fear, political will, and mobilization. Start by refusing to vote for anyone who puts the lives of you, your children, and your grandchildren in mortal danger.
Sorry for long post. But you asked and this is the most important issue of human existence. We have to get this right. Failure is not an option.