Science Briefs

GISS scientists are requested to write "popular science" summaries or "science briefs" to accompany and help explain their scientific papers in language accessible to the general public. This fable is a research brief to accompany several recent papers. Characters in the fable are imaginary, representing modes of thought rather than specific people, and are intended to address important climate issues.

Trial of the Century — Act II

Act II, Scene 1 (A Tavern)

Plump MIT-trained CO2 stirs his drink and looks at his watch. His earlier conviction for plotting the demise of Planet Earth (see Act I) was overturned by the Supreme Court, and a retrial ordered. CO2's beady eyes sparkle as he awaits the arrival of the evil twins from Planetesimal Decrepit. CO2 will defend himself in court, and he wants the twins to appear as witnesses in his defense.

Finally, they arrive: lanky Bigwind Geezer, from the backwoods of the Colorado region on Decrepit, and his brother, squarish Iceblock Geezer. "What a pair of bumpkins," CO2 thinks, as he greets them and they order beer on tap, but their appearance matters not for his purpose. "Thanks for making the trip and agreeing to testify."

Figure showing three line line plots of sea level, climate forcings and temperature over the past 400 thousand years
Fig. 1: Sea level, climate forcings, and temperature change for the past 400,000 years. For details, see Hansen (2005) "Keeling" presentation. Click for large GIF or PDF of figure.

"Surely," responds Bigwind, "we cannot let Prof. Quigley's nonsense go unchallenged. It is ridiculous to say that as the population of your brethren CO2 increases it will cause planet Earth to overheat, that storms and droughts will become more intense. What nonsense! The intensity of storms fluctuates naturally, in response to irregular cyclical changes of the sea temperature. Using the sea temperature I can predict wind speed with my weejee board!"

Bigwind pulls a weejee board from his jacket pocket, "Sometimes I get the wind speed almost right."

"Brilliant!" says Iceblock, raising his glass.

"Brilliant!" echoes Bigwind, raising his own glass.

Sophisticated CO2, not very amused, winces and interjects, "How will you respond if Quigley says that my CO2 brethren cause sea temperature to increase?"

"Nonsense!" fires back Bigwind, "Even if CO2 population doubles, it can cause only a negligible change, maybe one or two tenths of a degree."

"I agree," CO2 responds. "I have a theory. It is true that my CO2 brothers trap a lot of heat, but only momentarily. Mother Earth deals easily with the excess heat, by exhaling it in the tropics. But, Iceblock, how will you respond if Quigley claims that heat trapped by my brethren will cause ice sheets to melt and the sea to rise?"

"Nonsense!!" says Iceblock, leaping to his feet, "I am furious at Quigley for his stupid musings! I, Iceblock, am the expert! It takes thousands and thousands of years to have any substantial melting of ice sheets! Quigley must be reviled for his ignorant comments, which scare people unnecessarily! I have models, I am the expert, and my models show almost no change in centuries!"

Bigwind raises his glass: "Ho, ho, brilliant!"

"Brilliant!" chortles Iceblock, as he sinks back to his earlier mood. CO2's beady eyes roll, as he watches his bumpkin allies cavort, but his hard little heart is warm and beating. They will provide invaluable support to his diabolical plan!

CO2 realizes that he needs to keep effects of the mushrooming darkside CO2 population inconspicuous for another decade or so, until the Point of No Return is passed. His only concern is that Humanoids may become suspicious of growing climate changes. His stolid 'friends' from Decrepit will be an antidote, raising doubt and helping stifle any potential actions to slow emigration of CO2 from the darkside. Soon they will be strong enough in number to overwhelm Planet Earth, and he will rule the planet from Battlestar Barge, which he has secretly constructed!

Act II, Scene 2 (A Courtroom)

Judge: "The court is in session. The Supreme Court has ruled that the jury overstepped its bounds in using circumstantial evidence to convict the defendant, CO2. I shall dismiss the case, unless more direct evidence of guilt is presented."

Quigley: "Sir, I have direct quantitative evidence. It is obtained by comparing the current warm interglacial period, called the Holocene, which has existed on planet Earth for the past ten thousand years, with…"

Judge: "Ten thousand years! How can that be? Is this some sort of theory, like the Big Bang?" he scowls down darkly.

Quigley, uneasily: "Well, yes, sir. We compare the Holocene with the Ice Age twenty thousand years ago, when planet Earth was about 5°C colder. We know surface conditions then, with ice sheets covering part of the planet, and we know how much CO2, CH4 and N2O were in the air. The Holocene climate forcing of about 6-1/2 W/m2 maintains a 5°C warmer planet, implying a sensitivity of about 3/4 °C for each W/m2 of forcing"

CO2: "Objection! Such a sweeping conclusion cannot be drawn from a single comparison. What if the sun happened to be brighter during the Holocene, or perhaps the Earth was passing through a galactic dust cloud, which dimmed the sun, during the Ice Age."

Judge: "Objection sustained. I do not understand your claim, Professor Quigley."

Quigley: "Your Honor, this conclusion is not limited to a single time. I call my principal witness, the revered long-lived Yodyte, who has kept records for 400,000 years."

Judge: "400,000 years! Never mind. Yodyte may take the stand."

Quigley: "Yodyte, I understand that you have a record of the level of the sea for more than 400,000 years. Please describe your record and its accuracy."

Yodyte: "The sea rose and fell time and again, as much as 100 meters, sometimes rapidly, as much as 5 meters per century, usually falling more slowly. Fig. 1a shows the record, which my friend Mark helped construct. Short-term error is typically 12 meters, and there may be other systematic errors, but the amplitude of about 100 meters is reliable, as is the fact of repeated variations."

CO2: "But you cannot prove the dates that these changes occurred!"

Yodyte: "My records are imperfect, but dates are good within several thousand years."

Quigley: "Your Honor, the sea level change reveals how much ice was on land. When the amount of ice decreases, Earth is darker and absorbs more sunlight. We calculate the extra heating, the climate forcing, in W/m2. Now recall Exhibit 1 of the first trial, showing the population of CO2 and CH4 on Earth for the past 400,000 years. We can calculate accurately the climate forcing due to the gas changes (Fig. 1b)."

"Earth must be in energy balance on thousand year time scales within a fraction of 1 W/m2. So we can multiply forcing by climate sensitivity to obtain global temperature change. For climate sensitivity 3/4 °C per W/m2, we obtain the blue curve in Fig. 1c. The calculated temperature change agrees well with observed temperature."

Judge: "What does this mean? What are the implications?"

Quigley: "There are many. Climate sensitivity 3/4 °C per W/m2 is valid for the full period. The ice sheet and gas forcings account for almost the entire climate change."

Judge: "What caused the ice sheet and gas changes to occur?"

Quigley: "The ice sheet and gas changes tend to follow temperature change, because a warmer planet melts ice and drives gases into the air. But the resulting ice sheet and gas changes cause more temperature change. Indeed, these feedbacks, the ice sheet and gas changes, account for practically the entire temperature change of Earth."

CO2: "So any small forcing or 'noise' causes climate change! Climate can wander chaotically. I am innocent! You have not shown what causes observed climate change."

Quigley: "The instigator of past climate change is irrelevant to your trial and guilt. Yes, small forcings and chaotic fluctuations, given time, lead to large climate change. The geographical distribution and seasonality of sunbeams, altered by changes of Earth's orbit, are one important climate forcing, as discussed in the first trial. But your darkside CO2 brethren, emerging from the deep Underworld where they have lurked for untold millennia, cause climate forcing identical to the forcing caused by CO2 that climate change drives into the air from superficial layers."

CO2: "How so? Your own curve (Fig. 1c) shows less warming today than the CO2 population would imply, if your climate sensitivity were correct."

Quigley: "The sensitivity gives the equilibrium response to net forcing. The forcing by darkside CO2 has been added so fast that almost half of the response is still 'in the pipeline'. This has been proven. The warming 'in the pipeline' is one of the reasons that Planet Earth is drawing near the 'Point of No Return'. And the net forcing has been reduced about half by the cooling effect of dust and other particles belched and stirred into the air mainly by darkside CO2 immigrants, who lurch and cruise about Planet Earth's countryside. This has been proven by thousands of scientists, whose writings I introduce as testimony."

Judge: "Your formal charge that Planet Earth nears the Point of No Return refers to effects of three "inertias".

Quigley: "Thermal inertia of the ocean is the cause of the 1°F (0.5-0.6°C) additional warming in the pipeline. Energy system inertia, due to existing infrastructure such as power plants and vehicles on the road today, makes additional CO2 and still further warming inevitable. The inertia of ice sheet dynamics is the third.

CO2: "Balderdash! Quigley knows nothing of ice sheets! I call my chief witness, a true ice sheet warrier, renowned Iceblock Geezer!"

Iceblock Geezer: "Your honor, the ice sheets that ignorant Prof. Quigley refers to, on Greenland and Antarctica, are large blocks of ice. As Earth warms they melt a bit on their edges, but this tends to be balanced by increased snowfall. Like a large ice cube, ice sheets melt slowly and large sea level change requires thousands of years."

Quigley: "Does your model include the effect of surface melt penetrating and softening the ice and lubricating its base? Does it include ice streams transporting icebergs to the sea, the changes of these ice streams due to removal of buttressing ice shelves as the latter are melted by warming seas, and the penetration inland of effects due to thinning coastal ice?"

Iceblock Geezer: "Our models have parameters."

Quigley: "The question is how ice sheets will respond to continued immigration of darkside CO2 at a Business-As-Usual (BAU) rate, which, it is widely agreed, will cause added (global mean) warming of at least 2-3°C (about 5°F) this century. We can keep added warming below 1°C only by beginning to slow the immigration rate of CO2 this decade."

Judge: "Why is 1°C the critical warming level?"

Quigley: " With greater warming there is no hope of maintaining Earth, Creation, as we know it."

Yodyte: "In recent millennia, over hundreds of thousands of years, Planet Earth has warmed and cooled many times. The warmest times at most 1°C warmer than today, averaged over the world, were not so warm as to unleash large positive feedbacks. In the warmest times sea level rose a few meters above today's level, but it took time, as climate forcings were weak and changed slowly."

Quigley: "In contrast, if CO2 increases at a BAU rate, warming will be near 3°C at century's end, producing a different planet."

Judge: "A different planet? What do you mean? How do you know?"

Yodyte: "He means that local conditions will change so much and so fast that uncountable lifeforms will perish. There will be no ice on the Northern Seas. Humanoids are devilishly clever. They will survive. Some of them will thrive."

Judge: "Say more. What do you see in the future?"

Photo of calving from the Helheim Glacier in Greenland. See caption.
Fig. 2: Ice calves from the Helheim Glacier in southern Greenland in May 2005. Ice loss by glaciers in Greenland doubled between 1996 and 2005. (Photo credit: NASA/Wallops)
+ View large JPG.

Yodyte: "It depends on the Humanoids. If they follow a path with slowly decreasing immigration of darkside CO2, and if they clean other warming pollutants from the air, climate change will be moderate, within the range of recent millennia, with added global warming less than 2°F (1°C)."

Judge: "And if not? If BAU growth of CO2 and other gases continues?"

Yodyte: "Climate changes will begin to be more obvious. Everyday effects will be moderate at first, some beneficial, but the intensity of extreme climate events will increase. The Point of No Return will be passed within about a decade. Doom will be sealed for ice of the Northern Sea, many Northern lifeforms, and other lifeforms around the world."

"The ponderous ice sheets will change but slowly at first, raising sea level only several centimeters per decade, but as movement of these giant grinding glaciers slowly accelerates it will attain momentum that cannot be stopped. Our children and their children will face seas rising more and more rapidly."

"Business-as-Usual will yield 5°F warming by century's end. Such global warming will ensure eventual sea level rise of 50-100 feet. Coastal cities world-wide will be inundated, with the damage occurring in conjunction with intermittent storms. Untold millions of refugees."

Quigley: "It may require several centuries for the full effect to play out. That is unclear. The ice sheets have never been forced by such a large rapid rise of greenhouse gases and such a rapidly changing forcing. But ice sheet disintegration, under Business-as-Usual, will happen. The certainty is much greater than 99%."

Judge: "Is that the main story? Is there more to happen?"

Yodyte (with bowed head): "I feel a force. My vision is not clear. It comes to me only from my ancestors' tales, of times long, long ago. They told of a horrific early history, the seas warmed so much, carrying heat to the sea floor, releasing massive numbers of gas bubbles, which rose into the air and heated the Earth to a Hellish state. Almost all lifeforms were destroyed." Yodyte shuddered.

Quigley: "Yodyte may refer to the Paleocene-Eocene transition 55 million years ago, when warming caused release of methane from methane hydrates on the ocean floor. Or a similar event at the end of the Paleozoic 250 million years ago. Global temperature rose 6 to 8 degrees Celsius. Most of that temperature rise was probably due to the gases released from the sea floor. It is not clear how large a climate perturbation was needed to release the gases. Humanoid-caused warming could alter ocean circulation, carrying warmer water to the ocean floor."

Judge: "I saw the movie! The ocean caused Europe and the United States to freeze over!"

Quigley: "No, your Honor. That was science fiction garbage. I speak of science fact. True, in Earth's history there were times when ocean currents slowed, thus cooling the North Atlantic region. Feedbacks discussed earlier led to global cooling, so both the regional North Atlantic cooling and global cooling reinforced each other, yielding strong cooling in Europe."

"But now Humanoid global warming has opposite sign of the North Atlantic cooling. Global warming overwhelms the cooling effect of ocean slowdown, except for a while in a small part of the ocean. Europe will warm along with the rest of the world. I do not know why relevant scientists demurred from correcting the science fiction."

Yodyte (ignoring them and continuing to shudder): "I feel a force. Millions of the creatures of Creation are crying out! They cannot survive great rapid climate change."

Quigley: "95% of all species on Planet Earth went extinct with the great rapid warming at the end of the Paleozoic!"

CO2 (leaping to his feet): "Yes! But I will rule! New lifeforms can evolve!"

Yodyte: "Lifeforms of devils!"

Quigley: "Evolution after the Paleozoic required millions of years. Planet Earth could be desolate for untold generations."

Judge: "Evolution! Never mind."

Yodyte: "My forefathers beg us to preserve Creation for the seventh generation!"

End of Act II


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