This is the problem, if you have lots of ice, it reflects sunlight, run away iceage. If you loose all ice, you end up with a runaway heatbox. You also loose any buffering capacity in the system at the extremes. So temps in run away iceages can become extremely (mars level) cold. Think about a massive volcanic eruption during an ice age, temps can drop so low you will freeze all your CO2 out, and trap it under water ice and then all the plants die off too. In a hot box, temps just keep rising, until insects and other polinating species die off, (~55 degrees) and then all your plants start massive die off. The heat is also bad for smaller plants (grasses, bushes etc) that can't handle hot temps and direct sunlight etc. Then your soil goes and things just get worse. Massive die offs reduced O2, and flying things don't like that either, so even cold areas start dying off. Once the balance is shifted, it gathers pace and can certainly run away. Venus and Mars are great examples of "how bad can it possibly get".. Delicate balance. Anyone who has owned a fish tank, and has issues can attest. Bigger systems afford you more time to make changes, but require bigger efforts and more time to effect changes. There are climate deniers ("nothing is happening") and just skeptical people ("more evidence required"). I can understand skeptical, because there is lots we don't know and understand. However, it is quite possible by the time we get to extremely high confidence levels in models and data, it will be far, far too late. Also if you are skeptical, you should support increased funding and awareness of the issues. We need to get off coal and fossils fuels. They won't last for ever, and they will limit our quality of life even if CO2 and global warming wasn't an issue. But it is an issue. So is putting dark coloured solar panels over the deserts. So is manufacturing billions of panels with no recycling system, so is nuclear, so is hydro, so geothermal. There is also the other issue that there is probably enough CO2 in the air that we can't stop already extreme increases, and now have to account for 2-4 degree global increases in temperature in our life times and oceans rising 1-2m in our lifetimes. Global enviromental catasophy caused by CO2 is just one of the calamities in play. Plastics. Toxins. War (probably over fossil fuels). Economic collapse. Ecological collapse by over fishing, over farming, deforestation are all in play as well. It is likely several are going to coexist in the very near future.