evidence: Beyond that threshold, scientists have found, climate disasters will become so extreme that people will not be able to adapt. Basic components of the Earth system will be fundamentally, irrevocably altered. Heat waves, famines and infectious diseases could claim millions of additional lives by century’s end. [...] Though much of the synthesis report echoes warnings scientists have issued for decades, the assessment is notable for the blunt certainty of its rhetoric. The phrase "high confidence" appears nearly 200 times in the 36-page summary chapter. Humanity’s responsibility for all of the warming of the global climate system is described as an unassailable "fact." [...] Failure to act now won’t only condemn humanity to a hotter planet, the IPCC says. It will also make it impossible for future generations to cope with their changed environment.