Ward claims that most mass extinctions were caused by microorganisms rather than asteroids or comets. According to Ward, when Earth warms up enough that there is a reduced temperature differential between the poles and the tropic, we lose the driver behind ocean mixing. Without mixing, only the uppermost layer of the ocean remains oxygenated, and anaerobic bacteria that producing poisonous hydrogen sulfide gas thrive. The levels of hydrogen sulfide in the atmosphere eventually become lethal poisoning living creatures and shredding the ozone layer. "This is life killing itself off," Ward says.
Carbon dioxide, the cause of this catastrophic warming, has been supplied by volcanic floods that churned out enough CO2 to shut down ocean mixing. But thanks to the actions of humankind, the delicate balance that keeps Earth habitable is once again in danger. "All you need is enough [warming] to reduce the temperature difference between the poles and the equator, and the whole system goes down," Ward says.
Volcanic floods were better than we are at putting out the carbon dioxide (and they'll likely prove quite proficient at it again sometime in the future). Experts set 350 parts per million as the maximum acceptable level for atmospheric CO2 while we are already at 390ppm. Geologic events that wiped out life in the past raised the levels to 1,000 ppm. Of course, we are slower, but still effective since things are likely to get very ugly for human life along the way even at our slow pace. Most of us are unlikely to see the near complete anihilation of life by the hydrogen sulfide producing micro-organisms. Instead we will see the more near term and obviously anthropomorphic misery such as displacement, war and famine unless we can learn to cooperate on a global scale with common goals. If we do survive our own political self destructive behaviors and attitudes we will still have to deal with the loss of arable land and the rising sea changing the world's maps, but we will probably have air to breathe.
It is fairly clear to me that the earth's feedback systems do self-adjust to some extent, but extreme Gaianism is nonsense. Unless, you consider that the earth's systems are doing just fine even if one of the adjustments was to eliminate us. It is also fairly clear that living systems do tend to cycle with a self destructive phase as part of that cycle. Again, when the cycle starts over something thrives, even if we aren't there to observe.
Are there any real solutions: Probably not, but there are things that will make life better while it lasts. Nuclear energy production (fusion, if possible, but there are difficult waste issues in either type of nuclear power production), efficient solar energy, better use of microbes to produce food and fuel are a few potential improvements. All of these are currently untenable technologies. Hope is the driver that will make these technologies a reality. Sharing scientific know-how and cooperative research just might make them possible.
If we are complete Medeans and we don't have long term hope for improving this world, we won't do anything. If we are complete Gaians and expect the world will just take care of us, we won't do anything. We only remember the people who did something.