In a recent report published in science, Marcott et. al. have reconstructed the temperatures for the past 11,300 years. Basically covering the entire “modern geologic age” called the Holocene. This is quite interesting because it puts the modern climate change into some perspective.
Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history.
The average global temperature of the past ten years is great than 7500 years out of the past 11,000 (roughly).
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time.
Yes, there have global average temperatures warmer than this present. But the warming, the rate of temperature increase is just not possible without human caused warming.
“What that history shows, the researchers say, is that during the last 5,000 years, the Earth on average cooled about 1.3 degrees Fahrenheit–until the last 100 years, when it warmed about 1.3 degrees F.
The largest changes were in the Northern Hemisphere, where there are more land masses and larger human populations than in the Southern Hemisphere.
Climate models project that global temperature will rise another 2.0 to 11.5 degrees F by the end of this century, largely dependent on the magnitude of carbon emissions.
“What is most troubling,” Clark says, “is that this warming will be significantly greater than at any time during the past 11,300 years.””
This is why this study is so important. We aren’t talking about a little, local temperature change over, even a few decades. We are at the beginning of a global, long-term increase in temperature.
This kind of thing is NOT a natural effect. It’s not solar maximums. It’s not Milankovitch cycles. It’s not volcanoes or asteroid impacts.
All of those, non-human, effects have happened in the past 11,000 years. We now know this because this research would have seen it. There has never been a time in the past 11,000 years where the global average temperature has increased so rapidly.
Now, I freely admit (as do the authors) that the resolution of this work is between 100-130 years. Meaning that a huge spike in temperature could have occurred, but if the temperature had dropped back to normal within about 100 years, it would not appear.
If one chooses to think that our modern temperature increase is a transient phenomenon that hasn’t appeared in the past, then I challenge that person to develop a model in which non-human events could result in a global 2°C temperature rise and then dissipate the massive amount of heat energy that represents all in less than 100 years.
We’re talking about 25*20^22 joules here. Keep in mind that a 20kiloton nuclear blast is only about 8*10^12 joules of energy. So, the rough equivalent would be the heat energy from 30 billion 20-kiloton nuclear explosions.
Heck, even with the amount of carbon dioxide and other greenhouse gases humans are pumping out, it’s taken nearly 100 years just to get that 2°C increase. And that’s basically taking every piece of plant material since the Jurassic and burning it as rapidly as possible.
This work is quite convincing. Of course, the die-hard denialists won’t be convinced. They have a vested interest in not being convinced, either by being paid to be a denialist, because they just have to right, or because it’s elitists that say so. Whatever the cause, the majority of people are coming around and work like this continues to support the claim.
Humans are a direct cause of the average global temperature increases by pumping greenhouse gases into the atmosphere.