As concerns man-made climate change:

"The temperature of the Earth" is an ambiguous term that cannot mean anything.  At any given time it is possible to measure the temperature of some very small part of the Earth, such as, perhaps, a shot glass of water.  At that same moment, other temperatures of the Earth that could be measured will show a variation from the temperature of molten rock (1,300 to 2,200°F) to polar ice (32 to -76°F).  Daily variation of the same place on Earth can be 50 to 60°F.  Seasonal variation can be well over 100°F in high latitudes.  

Conceptually, we could imagine, but not actually measure, every possible place and thing, at every possible time through all the seasons, and then average these data.  To detect "global warming," we would have to modify these data to include the specific heat of every thing measured, as well as the latent heat of all the things that change phase such as water, which appears as liquid, vapor, and ice.

Conceptually, yes; actually, no.  Not possible.

Atmospheric science is presumably the scientific study of the atmosphere.  (I am proudly not an atmospheric scientist.)  If you use the scientific method to study something, you might presume to call yourself a scientist.  Calling yourself a scientist does not give you the privilege of using bad data to reach fuzzy conclusions and then scare people with the latter.  These folks are looking for about a 1°C change in "the temperature of the Earth" over the course of 100 years.

If you just look at the thing they are trying to measure and the tools they are using to measure it (including the accuracy of thermometers 100 years ago), you can reasonably presume that this particular science is not very scientific.  On my kitchen wall are three thermometers.  Two use technology vastly superior to what was available 100 years ago.  The third one uses fairly old technology.  They are 17 inches apart.  The room temperature is maintained by a state-of-the-art home heating system.  As I write this, they read 68.0, 70.2, and 73.  (Feel free to try this experiment at home.)  

If atmospheric science is not science, what is it?  It is the nearest thing to a religion, particularly for the liberal secular humanists, atheists, and agnostics of the left.  It has a pretty close copy of the concept of original sin and drips with guilt.  It is the lever that politicians on the left will use to change our economy, violate our constitution, and restrict our freedoms.  It is offered as the "big problem" that only "big government" or maybe "world government" can solve.

This stuff is "junk science."  These folks read ice core samples and tree rings the way fortune-tellers read tea leaves.  They start with the conclusion and search for the evidence.  Anybody who uses the term "settled science" doesn't understand science.  Science is never settled.  

I was an engineer for 29 years.  I have six patents in the field of heat transfer.  My bet is that I have measured more temperatures and studied more heat transfer than your average atmospheric scientist.  I'm also a combat veteran and a member of the American middle class, which earns me the right to be skeptical of junk science as a policy reference.  Every time these politicians have a "good idea," I pay for it, one way or the other.

In the case of man-made climate change, don't drink the Kool-Aid.  The quality of life is directly proportional to the per capita use of energy.  Far from being a pollutant, carbon is essential to life on this planet.  The most abundant forms of energy are still fossil fuels.  Federal meddling in the form of mandates and subsidies just distorts the market.  If you want to see the economy grow, get big government out of the business of picking winners and losers in the energy field.  It is a moral issue.  The fear of global warming is killing some people and making the lives of others wretched. 

What will the useful idiots say when the lights go out?  Can they virtue-signal in the dark?

Jerry Powlas has been a naval officer, engineer, and publisher and is the author of Red State Rebellion (available through Amazon).  He lives in the 'burbs of Minneapolis with his wife Karen.  When not there, they can be found sailing their boat somewhere on Lake Superior.