https://www.washingtonpost.com/climate- ... ford-lake/
tl;dr:
It simply is not true that what we're experiencing are the natural ebbs and flows that would have happened without our involvement.The sharpest sign of change was a surge in radioactive plutonium that started in Crawford Lake’s mud around 1950. The element rarely occurs naturally on this planet; it could only have come from nuclear weapon tests happening thousands of miles away.
Other shifts weren’t necessarily new, but they appeared at scales ten or a hundred times greater than anything the lake had seen before. A lighter form of nitrogen — a molecular signature of burning fossil fuels — proliferated. The amount of fly ash increased eightfold in less than five years. Acid rain, caused by pollution reacting with water in the atmosphere, diminished the calcite layers.
Still more sediments recorded irreversible losses. Certain microbe species were eliminated locally. The amount of elm pollen plummeted — a consequence of the invasive fungus that was decimating North America’s tree populations at the time.
All the while, greenhouse gas pollution made the planet inexorably hotter. The lake’s calcite layers became thicker during warm years; pollen grains show how the forest composition shifted to include more heat-loving tree species.
Average temperatures in southern Canada have increased about 1.5 degrees Celsius (2.7 degrees Fahrenheit) in this time. The globe as a whole is now warmer than it’s been at almost any point since the end of the last ice age.
These changes all are the result of what scientists call “the Great Acceleration” — the dramatic, simultaneous surge in almost every measure of human activity that started in the mid-20th century and continues through today.
The same evidence appears all over the planet, in every potential golden spike site the Anthropocene Working Group has examined. Peat bogs, ocean basins, the skeletons of coral reefs — even the ice of Antarctica has been permanently tainted by human pollution.
“What we have measured, in a very objective and quantitative way, is we are living in a world with conditions that are no longer within the last 11,000 years of natural variability,” McCarthy said. “The Earth is, in fact, fundamentally different.”
