Someone asked me this question on the Climate Change group:

"I am new to the front and I got stopped dead in my tracks by a Climate Change denier who showed scientific evidence that climate change is a naturally occurring phenomena and is actually LESS extreme than the natural climate change which has happened in the past, according to geological records. Help."

Here's my answer:

Great question.

• Yes, the climate is always changing. In natural cycles, it took thousands of years to swing between, but now we are pushing the needle in a matter of decades. Even evolution - which as a scientist he must be okay with - requires geological timespans to adapt. Such quick shocks are not conducive for survival - just ask the dinosaurs.
  

• Whether the current cycle is less or more extreme than natural ones is an irrelevant argument, as far as the consequences are concerned. What concerns us are the impacts to our civilization.
  
  Consider this. The Great Big Spot on Jupiter is a megastorm whose diameter is 3 times that of Earth, and has been raging for more than 200 years. It is by all accounts very severe and naturally caused. But it doesn't have an impact on our civilization.
  
  Even if current climate change were occurring naturally (which it isn't), we will face consequences like more and frequent severe weather, superstorms and megadroughts, rising seas and failing crops, refugee crises and mass extinctions. So unless his point is that naturally caused climate change magically will not have any visible impact, it doesn't negate the fact that we have to act.
  

• To bring up "scientific evidence" to counter the overwhelming consensus of scientists worldwide seems absurd, considering the fact that science proceeds with peer review. But let's see how far this rabbit hole goes.
  
  Case A: he implies that somehow thousands of scientists have missed a critical piece of evidence which singlehandedly overthrows their years of research. How likely is that an area of research that has been pursued for close to 50 years has missed such a basic observation that can be found with a Google Search?
  
  Case B: he is implying that there is a conspiracy of evil scientists who have banded together to deceive the world. They are crying wolf! Why though? If money, power or fame is what these rogue scientists are seeking, taking tenure at university seems like the most boring path to success.
  
  But let's take a gamble, in an informed way. Either the scientists are right or they are wrong. And either we believe them or not. And now let's look at the worst-case scenarios.
  
  If the scientists are right and we don't believe them: catastrophic atmospheric changes will threaten global civilization and cause mass extinctions.
  
  If the scientists are wrong and we mistakenly believe them: we would have spent a unnecessary money on decreasing pollution and finding new sources of energy.
  
  Which worst-case scenario would you prefer to be stuck with? And what if I told you the odds that the scientists are right is 97%, and the odds that they aren’t is 3%? Which bet would you take if you were a gambler?
  

• It's tempting to draw parallels between tobacco denialism and climate denialism. For almost 2 decades, tobacco companies argued in court that there is no conclusive link that cigarettes cause cancer. No one can prove that one fatal puff will lead to a cancerous mutation. And yet... a thinking individual who smokes cannot in good conscience say they are not gambling with the odds. This has exact parallels with asking the question "did climate change cause the accelerated disintegration of this iceberg"?

And as a final bonus, here's a crash course by Elon Musk on climate change.