Back in 1990, with 110 years of temperature records behind them, the world’s top climate scientists convened to put together a report on the state of the Earth’s climate. Working collaboratively, the fruits of their labor became the very first Intergovernmental Panel on Climate Change (IPCC) report. It definitively showed:
- there had been a global increase in carbon dioxide concentrations since pre-industrial times from ~280 parts-per-million (ppm) to 354 ppm,
- this was coupled with a global average temperature increase of 0.7 °C (1.3 °F),
- that the increase in temperature was being driven not by the Sun, volcanoes, or urbanization, but rather by the human-wrought changes to our atmospheric contents,
- and that this problem would continue to worsen unless carbon dioxide emissions were curbed.
Despite sounding the alarm, the past three decades have led to a far more dire situation. As identified in 2021’s 6th IPCC report, carbon dioxide concentrations now sit at 412 ppm, Earth’s average temperature is a full 1.3 °C (2.3 °F) above pre-industrial levels, and our global carbon emissions have increased to a new all-time high: nearing 40 billion tonnes of carbon dioxide annually, up from 22 billion in 1990. The best time to act was long ago, but the second best time to act is now. Here are the truths of the matter that everyone who’s vested in following what the science shows should know.
The Earth has really warmed since pre-industrial times, and the rate of warming is increasing with time.
The Earth, at present, is indisputably a warmer planet today than at any point in all of recorded human history. This isn’t because of the Sun; it isn’t because of Milankovitch cycles; it isn’t because of volcanic activity. It’s directly due to the human-caused emission of greenhouse gases, with the concentration of carbon dioxide being the dominant driving factor in increasing the Earth’s temperature.
The Sun outputs energy, the Earth orbits at a specific distance from the Sun, where it absorbs some of that sunlight and reflects the rest, and then re-radiates its absorbed heat back into space. If we simply accounted for these factors and ignored Earth’s atmosphere, including:
- cloud cover,
- greenhouse gases like carbon dioxide, methane, and water vapor,
- and the transparent-in-visible-light but absorptive-in-infrared-light properties of those gases,
we’d calculate that Earth’s average temperature should be 255 Kelvin (-18 °C / 0 °F). Instead, owing to these effects, Earth’s average temperature is 288 Kelvin (15 °C / 59 °F). The 33 K greenhouse effect is 50% attributable to water vapor, 25% due to clouds, 20% due to carbon dioxide, and 5% to other gases. Increasing the carbon dioxide level by ~50% over its pre-industrialization value is the primary driver of the recently observed warming.
It’s so significant that if we only look at global temperatures since 2000, the signal is robust, significant, and terrifying.
It took over 100 years from the time when global average temperatures began being measured back in 1880 before a robust, 5σ signal (with less than 0.0001% chance of it being a statistical fluke) demonstrated that the Earth was, in fact, warming.
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