Leef, It was probably hotter a lot more recently than 3-5 million years ago.
There have been many cycles of glaciation and meltoff over the last 3 million years. Initially, the cycle was about 50,000 years between warm periods, but about 900,000 years ago, it changed to about 100,000 years per cycle.
During previous interglacial periods, sea levels sometimes rose more than they have so far this cycle. During the last interglacial period about 100,000 years ago, sea level reached a peak 25 feet higher than it is now. I remember reading about a 65 foot higher peak sea level several cycles earlier. It is a good bet that there were some rather warm years back then, before we had record-keeping humans. And single years are probably not discernable in the geological record with the accuracy needed to make year-to year comparisons with the present.
That doesn't mean we aren't eventually headed for global conditions similar to 3 to 5 million years ago, before the current (just ended?) cycles started. But, we are probably not yet out of the global conditions that have been experienced in previous warm periods. We may have already passed the point where we are unable to prevent getting back to the conditions that existed millions of years ago. It takes time for global temperatures to reach equilibrium when there is a change in net heating or cooling effects. There is no question that we are in a heating-up period at the moment.
"If we could magically wave a wand and put electric cars in the homes of everybody in the U.S., in place of their cars with internal combustion engines, we would crash the electric grid when they tried to charge them."
That's not really true. There's now lots of evidence that the opposite should be the case, especially combined with energy efficiency and distributed generation.
With energy efficiency alone, I managed to reduce my primary energy use by 85% and the resultant loads can mostly be timed whenever I want them to occur mostly without batteries (just in vehicles), and 120% of the remainder is created on-site with solar on just one of my rooftops.
The advantages of electric vehicles of all sorts is you can choose to charge them when there is excess energy available and either not charge or feed energy back to the grid when there's a shortage. I charge when the solar on my roof is over-producing. I also pre-heat in the winter at the same time and also time my heating and water heating loads with the needs of the power grid.
There may (or may not) have been a couple of short-duration spikes at or slightly above our current level, but the last time is was consistently this hot was 3 million years ago.
"As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years.
In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly TEN TIMES FASTER than the average rate of ice-age-recovery warming."
NASA Earth Observatory
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This is from 2010. The warming since 1880 is now almost double, the 0.70C warming NASA was referring to.