Let us consider the details and explain why we are seeing a world with a high concentration of CO2, with all of its consequences, as inevitable, and why the current political and technological approach to the problem is largely inadequate.
The most effective way of looking at things is to consider the Earth’s atmosphere as a bathtub: it has a certain amount of CO2 in it; it gets filled constantly with more CO2 from human-related activity (mainly combustion of any material containing carbon, whether it is wood, fuel, coal, or other) and the occasional geologically-caused emissions (such as volcanic eruptions); and it gets relieved constantly through CO2 absorption in mainly three ways: by vegetation, by oceans, and by land. If the bathtub is filled faster than it gets relieved, it fills up, and the general level of CO2 in the atmosphere goes up; if the quantity of CO2 absorbed from the atmosphere is higher than the one emitted, the level of CO2 in the atmosphere goes down. This is pretty simple indeed.
It is important to note here that the three ‘natural’ methods of absorbing CO2 mentioned above are rather slow, and the one that is the most effective at absorbing CO2 over the long-term is actually the slowest (that is carbon natural sequestration by land). The problem with trees and vegetation absorbing CO2 is that they can be cut and used again, which does not really constitute an effective way of absorbing CO2 over the long-term, unless large stocks of flora are left untouched on Earth and are not subject to destruction by forest fires and by humans, whether intentionally or not.
Currently, the average annual level of CO2 concentration in Earth’s atmosphere is close to 400 ppm which is very high by the standard of the timespan of homo sapiens on Earth (last ~200,000 years), of the most recent Ice Age we are still technically in, and likely of the most recent millions of years, but not high at all in the context of the billions of years of Earth’s existence where we can find periods of exceptionally high presence of CO2 in the atmosphere largely above the 400 ppm level (some models even talk about 7,000 ppm for some periods millions of years ago…). This concentration level fluctuates over a certain year, sometimes below 400, sometimes above, but the average has been increasing steadily over the past several decades and is set to break through the 400-ppm barrier soon (if it has not already done so). The main contributor to this increase in CO2 levels in the atmosphere over the past couple of centuries is indeed human activity; humans, by their daily activities, are causing greater emissions of CO2 in the atmosphere which are not absorbed as quickly by the natural prevailing methods of CO2 absorption.
The difference today between emission and absorption exceeds 2 ppm per year; this means that, every year, the average level of CO2 in the bathtub that is the Earth’s atmosphere is increasing by more than 2 ppm. And this difference, this ‘delta’, is actually widening every year: we are pouring more CO2 in the bathtub, faster with time. We do not actually dispose of accurate data concerning the details, i.e. how much is actually emitted, and how much is actually absorbed every year by young forests, oceans, and land, as it is indeed quite complicated to measure these details accurately. What we know with more certainty is the resulting net increase of CO2 in the atmosphere year-over-year, in addition to general ideas of the pace of CO2 absorption by vegetation, oceans, and land.
And now here is the most ironic part about the entire political debate concerning the reduction of CO2 emissions: most efforts today aim at decelerating the increase in this delta between CO2 emission and CO2 absorption (which today slightly exceeds 2 ppm per year as we said) over the coming years. And this is the best this political discussion can hope to achieve if it succeeds. In other words, all what this tedious political wrangling we hear about in the news, with its low chance of success, in generally difficult economic times, can hope to achieve is a smaller increase in CO2 concentration by 2100 than if we do nothing. So instead of taking us from ~400 ppm today to (for example) 700 ppm by 2100, what this political wrangling can only hope to realise is a target of (again for example) say 600 ppm by 2100.
[To be continued].