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between 180 and 300 ppm...over the last ~150 yrs the top figure has risen to the level of 425 ppm, i.e. an amount equal to the entire High/Low range from the past ~1M yrs...and it's increasing monotonically as we continue to spew copious amounts of CO2 into the atmosphere. Also recall that JH's link called CO2 content the primary 'Forcing Function' of Global Surface Temps.

Now let's go to Dr. Roy Spencer's satellite recorded Global Tropospheric Temperature Data since ~1978...(see image below)...notice the amount of increase in less than 50 yrs?
...see the (increasing) trend?...think that won't impact coastal cities and established farming areas around the world?...if not, think again.

Don't be afraid to "Look Up"...and face Reality...your kids/grandkids will appreciate you acting like an adult.