This is utterly wrong!
You don't need to reduce your living space or reduce climate control to reduce your CO2 emissions. Just having higher standards for thermal insulation and heating/cooling of houses can reduce the energy consumption of the average crappy American house by 75% (note: almost all the buildings in the US have a very poor energy efficiency). Thicker and more efficient insulation layers in the walls/roof/floor, double glazing with good sealing for the windows, a condensing boiler (or better: a heat pump) for heating and hot water, a few thermal solar cells on the roof, and a reasonably efficient air conditioning: these things will probably add 10-15% to the total construction cost of a house, but will easily be amortized over 2 decades (just by the reduced energy consumption).
And regarding the other things like walking instead of driving, that's riduculous. Just begin by buying a car with a reasonable gas milage (hint: you don't need a 5000-lb vehicle with a 5000cc engine to go to work every day). And support an improvement of mass transit where it is sound (hint: using mass transit actually supports it).
Eating less meat, yeah, that's probably a good thing to do. But the good news is: you can eat better meat. Eat 2 filet mignon per week instead of 8 burgers.