so they claim nobody understands global warming or climate change.

1) Who told you scientists don't have a good definition of global temperature?

2) Do you you know how long it takes to complete one glacial-interglacial cycle? And do you know what are the range of CO2 level between a glacial-interglacial cycle? Do you know how long it takes for atmospheric CO2 level to increase from pre-industrial level to way beyond the level of last interglacial maximum?

3) Prediction is still inaccurate, but the records in the last 200 years or more are undeniable.

quote Trump: who knows the health care is so complicated.