Global warming
There is much misinformation about the normal temperature on Earth. Here is some science that refutes the lies:
Earth historical temperature has both long-term and relatively shorter-term variations. Long term variations last many millions of years and are called ice ages and warm ages. The shorter-term variations are called glacial cycles and interglacial warm cycles and are overlaid on top of the long-term ice and warm ages. Many will be surprised that we are in an ice age, but also in an interglacial warm cycle.
The first graph shows the long-term average global temperature view of warm periods and ice age periods:
Note that Ice ages vary in length, but 50 million years is pretty typical. Warm ages last much longer than ice ages.
The second graph shows temperature variations for the last 450,000 years in our current Ice Age which started about 10 million years ago, depending on exactly where you want to specify the start temperature from graph 1. (The temperature scale on graph 2 is the average temperature at the Antarctica glacier bore site, not the same as the average global temperature from graph 1):
The temperature for the current interglacial warm cycle from ice core data in Greenland is shown in graph 3. Note that the temperature always fluctuates and that the current temperature is not out of the normal range of fluctuations. Also note that on the lower left there is an error. Where it says “End of the last Ice Age” it should say “End of the last Glacial Cycle” because we are still in the last Ice Age, just in an interglacial warm cycle.
I frequently update this writeup to try to make it clearer. If you have a comment or suggestion, please send me a FR-Mail.