A new paper published in the Proceedings of the National Academy of Science (PNAS) speculates on major warming in our future. It has sent the gullible, alarmist press into a twitter of claiming that we must do something immediately. Trouble is, this very speculative paper says major warming may, might, could, perhaps occur sometime within the next few centuries to thousands of years.
Here is the abstract:
We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values. [full paper here]
What? Me worry? Dr. Judith Curry (retired Professor and Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology) opines: “A paper about climate outcomes on a millennial time scale would seem to be completely irrelevant to any conceivable policy. Even if our understanding of all of these climate processes were certain (reality check: we are dealing with deep uncertainty with regards to future climate outcomes), geologic and solar wild cards will almost certainly come into play to produce climate surprises.”
The horrid hothouse described in the paper is actually the normal temperature for planet Earth according to geological evidence (except during ice ages). Current global average surface temperature is about 57°F (14°C) versus a “normal” temperature of 77°F (25°C) as shown on the graphic below:
During times of “normal” (very warm) temperatures life was abundant and robust. If (or when) we return to those temperatures we will have to adapt as it gets warmer and sea level rises.
My impression of this paper is that its sixteen co-authors are taking advantage of the political climate to get their names on a paper published in a professional journal, something very important to academics.
On the other hand, we might first have to adapt to colder temperatures. Scientists who pay attention to solar cycles have noticed that the magnetic strength of the sun is declining with each cycle. This means that more cosmic rays will enter the atmosphere and produce more clouds and hence more cooling. The graphic below shows the gradual decline of temperature during our current inter-glacial period and the cyclic nature of warm-cold periods. Speculation is that we are about to enter one of the cold spells of the Holocene or even that the relatively benign inter-glacial period is coming to an end.
Here is an example:
The Next Ice Age
By Dr. S. Fred Singer
While most people still worry about global warming, I am more concerned about the next Ice Age. A glaciation would present a serious problem for survival of our present civilization, akin to a nuclear winter that many worried about 30 years ago.
Natural warming of the Earth reached a peak 65 million years ago. The climate has been generally cooling ever since. Antarctic ice sheets started growing 25 million years ago. In the last 2.5 million years, the Earth entered the period of Ice Ages [the geological name is The Pleistocene] and has been experiencing periodic glaciations where much of the land was covered by miles-thick ice sheets.
There have been about 17 glaciations, each lasting approximately 100,000 years, separated by short inter-glacials lasting about 10,000 years.
We are approaching the likely end of the present warm inter-glacial, called the Holocene. It’s time to prepare for the next glaciation to see how we can overcome it – or at least postpone its onset. Read more (Singer is a physicist and a Professor emeritus of environmental science, University of Virginia.) I’m with Fred.
If Dr. Singer is right, then we all should triple our “carbon footprints” assuming you believe that carbon dioxide emissions play a significant role in controlling global temperature.
An article in Science 2.0: “Not As Scary As It Seems: Planet At Risk Of Heading Towards “Hothouse Earth” State” [link] Gives a summary and comments on the paper. They say “Hothouse earth does not make us extinct – still a very habitable planet” and “In short, it is a hypothesis not yet supported by evidence.”