There is no optimum or correct global temperature nor does anyone believe there is. LIterally NO ONE says there should be. Certainly no scientist. WHAT IS IMPORTANT IS: the CHANGE in the overall climate. The OVERALL temperature is increasing globally, but individually in locations the climate may change to a WARMER OR A COOLER environment locally. The climate is a complex interaction between many sub-climates. Climate change is what happens when the overall global temperature increases leading to changes locally which may cause some places to cool. Here's how (for example): The gulf stream is what brings warm water and warm air up from the Tropics to Western Europe. That warm water causes the climate of western Europe to be WARMER than it would be WITHOUT the Gulf Stream. Global warming is causing the Greenland Ice Sheet to melt which is putting cold FRESH water into the upper part of the Gulf Stream. The reason the Gulf Stream exists is because of salinity and temperature differences. If you pump a lot of cold fresh water into the gulf stream (mostly saline water) you can destabilize the Gulf Stream. This is already being observed in the water temperatures. This will ultimately lead to a massive shift in Western Europe to a COOLER climate which will, of course, decimate their agriculture etc. and lead to lots of bad things. But locally the area gets COOLER while the globe overall warms up. (It's a big place). Finally: the real problem will be the impact it has on our economy, agriculture and other resource availabilities. Same answer. No "proper" level of CO2. Humans have evolved in a world with a global set of climates that have remained largely stable over the last 14,000 years since humans settled in towns. Changing the climate QUICKLY after we've only ever known the present climate will result in problems. Again it is the CHANGE, not the absolute value. CO2 is treated as a pollutant in order to track it's concentration changes in the atmosphere. While the CO2 doesn't cause us to be physically ill like many pollutants, it WILL PROBABLY LEAD TO SEVERE DAMAGE TO OUR ECONOMY AND SOCIETY, so it's still problematic and needs to be tracked. What is actually measured in climate change science is the TEMPERATURE ANOMALY. NOT the temperature. So they use a baseline (although I have no idea where you got your numbers, that is usually not the baseline used for anomalies), but you get the point. The 1850's is thought to be the time when climate change really started to ramp up. With mass industrialization.
We can only control ourselves. Last I checked we cannot force China to do anything. Besides they actually have put some effort in on environmental regulations. Not enough, obviously. And if they put in too many we'll move our manufacturing to someplace that doesn't have it because we value cheap goods, not safe worlds.
Not everyone is. Most of us do. Then we have to be insulted by people who don't.
