There's definitely reason to be optimistic.
Emissions have started decreasing majorly in Europe [1], slightly in the USA [2], and are even leveling off in China [3].
Those three entities account for half the world's emissions.
Solar power has become cheap enough now that it's reasonable for developing countries (especially India) to rely on it heavily as they become fully electrified.
The problem is the real, unbiased, can't be faked data shows that the CO2 level is rising the most it has in recorded history. It has jumped 4 ppm in the last year alone [1].
3.75ppm, but yes - to be clear, worldwide emissions are continuing to increase, so the CO2 level should be rising by more and more every year.
If we can level off our greenhouse emissions (and we're very close), the CO2 level should continue to rise each year, but at a roughly-constant rate.
And if the world can get approach net-zero greenhouse emissions (a reasonable goal for 2050), the CO2 level should stop growing.
And then, we would need a few centuries of negative greenhouse emissions to get back to pre-industrial temperatures.
I suspect we'll never bother to do this.
According to the NOAA link I provided the CO2 concentration at Mauna Loa rose from 402.80 ppm in June 2015 to 406.81 ppm in June 2016 (most recent data) which is 4.01 ppm in a year :(
I think you mean the growth rate of CO2 emission is starting to level (actually looking at the data not even this is true), not growth of CO2. We are still headed for disaster if the CO2 goes up by 4ppm every year. I see no sign that emissions of CO2 are slowing, or that we are doing anything serious to stop emitting GHG. Just look at the growth of CH4 which is continuing to increase [1].
No. Data that comes out of a political process where people can claim that they are reducing CO2 emission is a lot more suspect than data that comes from actually measuring the CO2 level in the air. This is how we can end up with such contradictory data - on one side there is a vested interest that says emissions are going down, while the measurement of the actual CO2 emission rate is going up.
The reason that the data is 'contradictory' is that the level of CO2 in the atmosphere is the integral of the emissions over time (minus the amount that gets sequestered by greenery and the like).
Even if the emissions level off fully, the expected amount of CO2 in the atmosphere will grow linearly. Emissions need to decrease to less than the rate of sequestration for the total CO2 in the atmosphere to shrink.
There's no contradiction: atmospheric_CO2 = integrate_{0,today}(emissions - sequestration)dt.
Yes the level is an integral, but the growth rate is a derivative. The growth rate measured in the atmosphere does not match the negative growth rate the political process is claiming.
Ultimately what matters is the absolute level of GHG and there is no sign this is going down anytime in the foreseeable future unless we make some major and very drastic changes.
> The growth rate measured in the atmosphere does not match the negative growth rate the political process is claiming.
The political process is claiming a negative growth rate in emissions (ie, the second derivative of the atmospheric levels, or the first derivative of the change in the atmospheric levels).
In other words, the growth of the growth in atmospheric CO2 levels is decreasing.
1. http://www.esrl.noaa.gov/gmd/ccgg/trends/