fig tree wrote:The pre-industrial level of CO2 is thought to have been about 280 parts per million. Now it's about 390 parts per million. We also have good evidence that it's there because we put it there. ... It's clearly our doing.
Within the larger scope, CO2 levels were ABOVE 1,000ppm for 100s of millions of years.
Currently they are at about 390ppm. 390 today vs 1,000 (and as higher as 7,000 in Cambrian)!!!! It actually seems like we are LOOSING CO2 at an alarming rate. That should be a bigger concern. See the graph.
In a lot of what you're quoting, there's a kind of unstated argument that runs sort of like this. If there have been big changes that don't have to do with human beings adding CO2 to the atmosphere, then we can reckon that this time too might have nothing to do with us. But this is just sloppy. Even assuming climate varied as described (which seems incorrect) we'd still have a problem.
Current CO2 levels 390ppm.
They have stayed above 1,000 ppm for hundreds of millions of years, and in some case reached 7,000ppm.
What caused such increase and decrease (in Cambrian after going to 7,000 it fell to about 4,500ppm again) ? If nature could do that at those times, it can do again.
Do rising atmospheric CO2 concentrations cause increasing global temperatures, or could it be the other way around? This is one of the questions being debated today. Interestingly, CO2 lags an average of about 800 years behind the temperature changes-- confirming that CO2 is not the cause of the temperature increases. One thing is certain-- earth's climate has been warming and cooling on it's own for at least the last 400,000 years, as the data below show. At year 18,000 and counting in our current interglacial vacation from the Ice Age, we may be due-- some say overdue-- for return to another icehouse climate!