Sure we can. There are multiple
proxies for rising temperature rising such as melting ice caps, changing migration patterns, changing sea levels, the bleaching of coral reefs, the frequency and severity of extreme weather events (droughts, floods, blizzards, tornadoes, hurricanes), changing ocean currents (surface and deep water temperatures, current directions and speeds, and salinity levels), something called phenology (the date of the first winter freeze and the spring thaw, when trees bud and lose their leaves, the behavior of various insects [apparently the rate at which crickets chirp is a reliable indicator of current temperature]. These are all changing consistent with warming of the planet. It isn't necessary to know the before and after temperatures.
Actually, some people are doing something about it. Our home went solar about nine years ago, and we now get our electricity for free without producing greenhouse gases. We still have heat and air conditioning, and charge our phones with solar power. Our hot water comes from solar heating, which has reduced our propane consumption to about 1/4th of what it was.
We actually collect more power than we need, which all goes to the local power company, allowing it to reduce its need to burn fossil fuels. Our carbon footprint might be less than zero if this offsets what we produce burning propane and gasoline.
If this is a hoax, it's been a very profitable one. One need not be interested in climate change to be interested in free power once the system has paid for itself.
It's not necessary to end fossil fuel burning, just reduce it sharply.