Solutions to global warming and all three conditionals

Compare the three conditionals. First: If we use solar energy, we will cut costs (real future). Second: If we used solar energy everywhere, we would cut emissions a lot (imaginary present or future). Third: If we had used solar energy earlier, we would have cut emissions already (imaginary past). When describing solutions you can mix should, could and would: We should plant trees; this could slow the heating. An essay follows the pattern problem – cause – solution – conclusion, and each part can include one or two conditional sentences.