Current CO2 levels have not been measured, either directly, or indirectly, for the last million years.
There is no way that scientists can determine how much warming there will be.
Clearly there will be warming, but at the moment we cannot say how much.
Part of that is not being able to predict how much we'll be able to cut back CO2 increase.
Another part is not having any model to determine what tipping points will be reached along the way -- such as permafrost melt releasing large quantities of methane.
No. Deniers like to claim things are "cycles", but they usually have no idea what is meant by something being a cycle. Undoubtedly there are real cycles that contribute to climate, but not to any extent that they could be used to predict climate change.
Most importantly, greenhouse gas emissions are NOT cyclical, so ignoring those will doom the forecasts to failure.
Cycles yes, regular, no. The identified "cycles", such as the PDO and El Nino can take at least a range of 0-20 years to complete. Solar output is a relatively minor variable with pretty regular cycle length, but wildly varying magnitude.
Yes we have AMO,PDO,ENSO,QBO,NAD,AO,PNA. these are the ones we know about, there might be more, and of course we have solar sunspot cycles, and in the long term planetry orbital changes (milankovitch cycles)
All this makes predicting climate in the future difficult, as you have to accurately weight each cause, and at the moment they cannot even forecast our climates sensitivity to CO2.
So at the moment predicting future climate is much like guessing.
You do have to remember we didn't have technology as advanced as today. We cannot 100% predict climate change but we have small speculations. The reason being that we're having trouble predicting weather patterns and jumping so far ahead as to predicting climate change seems like a giant leap. Anyways, I hope my answer shall suffice
They may be better able to predict when the warming speeds up and slows down, But as long as humans burn fossil fuels, the carbon dioxide will dominate the trends.
It does't look like it. Some people think so, but most scientists think not.
