It is critical that we have a viable concept of how to develop alternative energy sources before we exhaust the fossil fuels which are needed to develop the alternatives. The ecosphere of the earth is a complex system, its analysis is extremely difficult, and our ability to anticipate sudden chaotic excursions from the norm is very near zero. I think we should anticipate both catastrophic warming and cooling. There is convincing evidence that global icing occurs every 10 to 15 thousand years which means we are due for one; however, we have tweaked he system by the addition of CO2 and can't be sure which way to lean or how fast either catastrophic extreme will develop. I believe most scientists are telling us what their honest analysis of the data is suggesting to them. Predicting the weather on a daily basis is difficult enough; predicting climate trends is way over our heads, but still we must try and we should hope to be right now and then.
Take a look
here for how heavily weighted our energy production is in favor of fossil fuels. It is surprising how small the contribution from hydrothermal and wind is. This table reveals at a glance that developing the alternatives before we run out of fossil fuels is strongly essential. Energy Production Ratio (EPR) of each new source must remain above unity (e.g., the energy production from one unit of coal must always be larger than the energy required to make it available to the furnace that uses it) and the larger the better. Not all coal reserves meet this requirement; I'm not sure about petroleum reserves. It is not obvious that advocates of each of the alternatives has really grasped how difficult the transition to alternatives is going to be; emotional hyperbolism will not help. We are all in this single lifeboat; if it must be rocked, do it gently.