I heard that El Nino is causing the unseasonably warm weather where I live.  Today, high clear blue sky, temperatures in the forties Fahrenheit, less of a December, more like the second week of November.  Climate change deniers contemplate a blizzard in March and call it a refutation of humanity-caused climatic eventual doom.  It's cold, I slipped on the sidewalk and strained my back, therefore there's nothing to the idea of a Greenhouse Effect coming our way from air pollution.
     Venus, Earth's nearest planetary neighbor, seems to have had a runaway Greenhouse Effect going on for millions of years, making the temperature in its mostly carbon dioxide atmosphere hot enough to melt lead.  I've never heard or read why this happened, but I did read several years ago in Astronomy magazine about how Venus, Earth, and Mars, between three and a half to four billion years ago, all had planet-spanning water oceans with scattered land masses.  A traveler in a spacecraft visiting our inner Solar System in those years would've seen three planets with viable life potential, all starting out using the same deck of cards.  The traveler could've landed on all three worlds, collected soil, rock, and primitive bacteriological samples, then gone away to visit other star systems.          
     A descendent of that traveler, journeying in a far more sophisticated ship, visiting our Solar System now, would find Mars cold and dry (though underground water and evidence of water flows have been discovered), Earth abundant with life, still possessing its oceans, and Venus a hot cloud-covered hell with sulphuric acid rain and a day lasting longer than its year, so slow is its rotation.
     What happened to these worlds that were so similar at one point?  Time's passage causes divergences in a single human lifetime; one doesn't necessarily end up doing what one thought of doing early in life--at the age of ten I decided to become an astronomer, but didn't.  Divergences over millions and billions of years are more pronounced than we, in several decades, can achieve.  Mountains rise up and flatten over hundreds of millions of years, but to Earth's life perspective, these are like what to us would be periods of a few years, when, for instance, we spend some seasons with friends, but later on never see them again.  In other words, the Appalachian Mountains used to be very hard to climb.
     Venus and Mars had oceans, Earth still has a planet-wide ocean with several names, but there were times when atmospheric and local stellar conditions made Earth's water supply do strange things, like the period when the entire planet was covered with ice, a cosmic cue ball.
     Climate change deniers are right when they say that the planet's environmental conditions alter over time, having nothing to do with our actions.  They're wrong when they claim that curbing greenhouse gas emissions is futile and only hurts business.  In time, if their belief about this prevails, their descendants will find it impossible to sell their products to dead customers.
     Earth, fortunately, before its destruction by the growing red future Sun, will survive us.

                                                                             Vic Neptune