This question was asked on Quora, and here’s my response: 
There are a couple of reasons people are reticent to “believe” in climate change. 

First, belief comes in many flavors on the time spectrum.  It is one thing to believe that if you step off a curb into traffic you will, within 1 second, be smashed by an oncoming bus.  Or, to keep a climate themed analogy, it’s easier to respond to someone saying, “You’d better put on a jacket… the storm’s coming!” when you can see clouds rolling in and moving rapidly toward you.  
It’s another level to “believe” that if you control your caloric intake and exercise, you will lose 40 lbs.  The goal is a long way away.  What is the goal of believing in climate change, and how far down the line is the reward?

Beyond time spectrum there is effect on the individual.  For anyone who reads my answers regularly, you know that my definition of belief involves “actions taken with the intent of arriving at a desired state.”   Use the previous examples and you see direct links between acting on a belief about the impacts of traffic or diet, and a desired state for the person doing the believing. (Surviving, and achieving a goal weight.) 

So in the case of climate change, what “belief” should one act upon to get to what desired state?  And can anyone clearly say that acting will achieve the desired state?  It is largely unknown.  

That said, appeals to people to act upon a belief in climate change are similar to appeals to act upon a belief in an after life.  No one desires to die under the terms of a climate apocalypse, and a vast majority of people want to believe in life after death.  Both, you see are “beliefs” based on a feared outcome. 

The trouble arises in asking, “What actions should I take NOW to achieve the desired state, and what guarantees can you provide that taking these actions will achieve taht state.  Religious charlatans know they can pry all kinds of money and devotion out of people afraid of dying, and while I “believe” in climate change, I’m hesitant to fall prey to similar charlatans promising relief if I only contribute to their pet project.