Q4.16. projections of future climate change vary widely. what is the primary source of uncertainty for how much earth's climate will warm by the end of the century? a) climate models themselves, which can't accurately predict weather and therefore cannot make reasonable forecasts of future climate change b) uncertainty from natural variability in the climate system (el niño-la niña cycles, volcanic eruptions, etc.) c) emissions uncertainty, which is uncertainty about how extensively people will use fossil fuels in the future d) climate response uncertainty, which is uncertainty about how to model feedbacks and other aspects of the climate system q4.17. which of the following statements about thresholds and abrupt climate change is false? a) there are thresholds in the climate system that, once crossed, can produce large, rapid changes. b) negative feedbacks that dampen the effects of small changes will produce abrupt, large climate change c) climate proxies have recorded multiple examples of abrupt climate change in the past. d) climatologists predict that reversing the effects of "tipping points" might take centuries or longer.