claim: “[Carbon dioxide] just crossed 400 parts per million, and high-end estimates extrapolating from current trends suggest it will hit 1,000 ppm by 2100.
evidence: Research suggests that upon reaching about 20–25% (hence 3–8% more), the tipping point to flip it into a non-forest ecosystems – degraded savannah – (in eastern, southern and central Amazonia) will be reached.