It can be hard to convince someone that the state of the natural world is changing. This can still be hard even when the change is occurring fast enough to see it with your own eyes. What you need is a spectacle, an "in your face" demonstration that there is a problem and it is happening to us, now. Pictures of melted glaciers aren't enough, it has to be present on your doorstep.
For a government that is so opposed to any government policy on climate and the environment, I propose this demonstration:
Step outside your door and breath in that clean air.
Is this not enough for them? Ok maybe I need to remind the reader of some history.
In 1935 the Americna West was in crisis. An influx of farmers had for decades been abusing the soil (to some extent unknowingly) to grow their crops. On March 21, concerned politician Hugh Bennett was informed that a gigantic dust storm was sweeping east. He timed a speech to Congress to finish as the storm entered into Washington D.C. itself. His fellow politicians could no longer ignore the news reports, they had been forced to see with their own eyes.
Later though people knew that our rivers were being choked with waste, nothing happened until in 1969 the Cuyahoga River actually caught fire. Though not as present, the obsurity and the shame of a river catching fire spurred action that has cleaned up much of our waterways and other environmentally impacted regions. Similarly it wasn't until Los Angeles had become a national joke for its air quality that action was taken to improve it, including instituting the highest vehicle emissions standards in the country.
Why do I bring up these events from the past? Because if you want to know why the government should be involved in environmental policy, the large "in your face" example is that the environment is cleaner today than it was when we let industry run amok. The fact that dust storms, burning rivers, and haze-filled skies aren't daily problems anymore is a testament to that.
Famously China still faces these problems and so do other developing nations, and there is still much to do, both here and abroad. But if I were Hugh Bennett reincarnate, I would throw the windows of the Capitol building open and let in the clean air as a showcase of why we MUST keep fighting for our environment. Breath deeply, because our predecessors have fought so that you can. And don't forget or abandon their work.