Archer, The Long Thaw's conclusions

11: sea level | 12: carbon levels | Epilogue-what did we do? | commons | optimization

Water world: Why Europe cares more about abrupt climate change than the USA.

11 Sea level and the deep future,

137-174.

"sea level estimates from the past."

"Ancient coral reefs and relic beach deposits attest to large changes in the sea level associated with past climate changes."

Barbados, relic reefs rising up faster than se level (due to tectonic forces) has been advancing.

"oxygen isotopes in Ca CO₃ shells deposited in the deep ocean also carry information about ancient sea levels."

137

20,000 years ago sea level was 120 meters --360 feet lower than now as water was tied up in Euro-American ice sheets when temperatures were 5-6˚ C lower than today

137

"During the last interglacial"

120 millennia -- 120,000 years ago ∆ by Earth orbital variation

"sea level was 4 to 6 meters (12-18 feet) higher than today."

Carbon dioxide levels were 280 ppm

There were no everglades and the Key Largo limestone barrier reef was flourishing with an extensive back reef zone.

3 million years ago in the Pliocene -- ice sheets were smaller in Antarctic and sea level was 20-25 meters (or 60 75 feet above today's) higher than now.

in the Eocene 40 million years ago it was 75 meters 225 feet higher 4-5˚ C warmer (138-139)

(Miocene marine transgression flooded the central Valley of California, no Florida nor Mississippi River valley.)

138

Temperature was 2˚ C warmer than now --- 3 million y a Pliocene

139

"Sea level in the past varied clearly and strongly with changes in global average temperatures."

139

from a 1/2 or .5 meter to 50 meter shift can be anticipated from the current GW

140

[it is a matter of how slowly the sea level responds to ocean thermal expansion and melting of land-based glaciers.]

"thermal expansion of the ocean" contributing to a quarter of a meter in rise

140

"melting land ice could eventually increase the sea level by perhaps 50 meters (150')

"Greenland however is close to the melting point."

141

Uncertainty

"No one predicted the explosion of the Larsen B ice shelf (antarctic)" 3/5/2002

141

Greenland's Jacoshavn ice sheet is accelerating movement by two times since 2002

142

West Antarctic ice sheet "would raise sea level by about seven meters." 21 feet

142

Heinrich events "raising sea level several meters within a few centuries."

"if such a collapse should start it would be impossible to stop."

142

melting ice "lubricates the bed" of a glacier " to lose its footing and plunge into the sea"

142-143

"The surface sends heat down to the base by means of flowing melt water." mulleins

143

"were it to melt" 5 meters as opposed to 7 meters for WAIS (West Antarctic Ice Sheet)

143

"There are five ice streams draining the WAIS into the Ross Sea."

"An ice sheet in this configuration may be susceptible to a runaway collapse into the ocean."

144

The Ross ice shelf sitting on a barrier of land as it does, acts as a barrier or dam to WAIS

144-145

"that would be difficult to forecast in advance, and impossible to stop when underway."

145

"if an ice sheet can collapse in a century as it has in the past, it could do so again in our century." [Heinrich events during the melt water pulse of the Laurentide de-glacial]

145

"but atmospheric CO₂concentration has never gone up as quickly as it is now."

146

"If the models are too slow, the forecast is too low" for sea level response to the >

146

2000 GtonsC/ 1000 years to 5000 GtonsC/10,000 years to melt the ice

" a 2˚C warming of the global average is considered to be a sort of danger limit benchmark."

146

"would remain so for thousands of years." translating into a 30 foot sea level rise

147

"It's only real estate after all."

"The 2.2% of the land surface that would be flooded by 10 meters of sea level rise is currently home to about 10 percent of the world's population."

"These properties must have a higher average value of the human race." 10%

147

"Economically, it would mean that this loss would be equal to about one year's worth of economic production . . . .

147

"then the economic hit is only 1% of GDP per year, not too expensive at all."

"The flaw in this reasoning is that we can not really buy back the land surface for its economic trading value

"Every hear the average American emits enough CO₂to ultimate flood 100 square meters (300 square feet x 300 sq. feet), almost 1000 square feet, the size of a luxury Paris apartment."

"the long-term carrying capacity of the planet"

"The selling price is short-term convenient energy. The clearest long-term impact of fossil fuel CO₂ (burning) release may be sea level rise. . . "

"We have the capacity to ultimately sacrifice the land under our feet."

148

12 Orbits, CO₂, and the Next Ice Age

149-157

in 1896 Svante Arrhenius "was interested in explaining the cause of the last ice age"

"So the landscape offered no information about the longevity of warm climate intervals such as our, only an ominous drumbeat of glaciations in the past."

149

"the ratio of oxygen-18 to oxygen-16 in ocean sediments." reveal the extent and duration of ice ages' cooler temperatures

glaciations persist ten time longer than interglacial warming periods based on past isotopic evidence.

149

"the orbital cycle called the precession of the equinoxes, which has a half-cycle time of about 10 millennia (10,000 tears)

At the end of the line?

150

pollen grains and O isotopes role in the glacial 20,000 years ago for predictions

150

120,000 years ago the ppm = to 280 ppm (pre-industrial levels)

"If it wasn't a drop in CO₂ (levels) that caused the ice sheet to form, the other usual suspect would have to be a change in the Earth's orbit."

for the last 800,000 years [Natural cycle] the amount of "northern hemisphere summer sunshine"–at about 65˚ N latitude–"gets dimmer than a particular trigger value, the amount of ice on Earth grows and the sea level falls..."

"Summertime sunshine…sue seems like the important factor." in ice nucleation

150

"about three thousand years from now." the summertime sunlight at 65˚N latitude will be approaching "trigger value" for an ice accumulation (dimming)

151

the trigger model suggests a persistence of the warm interglacial -- though this is open to doubt based on actual variables

151

"but not without a lot of uncertainty."

152

"its too close to call" ? the ice age coming or warm interglacial persisting ?

152

if we miss the "glacial express" this time 50,000 years from now the chance comes around again

"less variability in solar forcing, than usual"

a nearly circular elliptical orbit makes little difference in N hemisphere summers while a more elliptical orbit makes for a cooler summer when the N hemisphere faces the sun

153

"interplay between the tilt (variable 21-25 angle of declination to the plane of the ecliptic) of the Earth and the elliptical orbit (distends)"

153

"it's about the same distance to the Sun all around the orbit"

"he last time the Earth was in this configuration was about 400 millennia ago (400,000 years ago)."

"The interglacial period at that time was about 50 thousand long."

153

CO₂ in our interglacial started out high, then dropped, heading upward again about eight thousand years ago (Younger Dryas?). That is the uptick Ruddiman blames on human agriculture." having liberated methane and carbon from soils & deforestation

154

"Also the ratio of carbon-13 to carbon-12 in atmospheric CO₂ through the rise of the last few thousand years seems to indicate that the CO₂ did not come from cutting trees, but rather from the oceans."

∆ "humankind has the potential to take control of future ice ages."

154

delaying the onset of glacial formation by doubling the CO₂

154-155

"The ocean stores enough heat to average out these extremes to some extent."

155

"The long lifetime of fossil fuel CO₂ in the atmosphere means that human activity will affect the trigger sunshine value for a long time into the future."

156

"the impact we have had on glacial cycle seems to be relatively small."

"We have released about 300 Gtons of carbon since 1750,"

if we burn 2000 Gtons C we stave off glaciation for 50,000 years

"If the entire coal reserves were used (5,000 GtonsC) then glaciation could be delayed for some,...half a million years."

"on the surface of it, this would seem like a good thing"

156

"The potential dangers of warming are immediate [the benefits too far out]

157

"The practical implication of the trigger model is that natural cooling driven by orbital variation is unlikely to save us from global warming."

157

Epilogue Carbon Economics and Ethics

158-174

"Humankind has the potential to alter the climate of the Earth for hundreds of thousands of years into the future."

158

shift in fuel sources over the last three centuries:

1. 18th wood [charcoal (and coal)]

2. 19th coal

3. 20th oil and gas

"In the long-run, it won't be hard again."

158

"CO₂emission is closely tied to economic and military supremacy in our world."

159

"much larger cuts [than 6% below 1990 levels] would ultimately be required to stabilize atmospheric CO₂."

159

Common property

The chemistry of the atmosphere is a classic example of something called the the tragedy of the commons."
159

"a degree of global cooperation"...."that humankind has never before achieved"

159

CFCS, Freon phase-out "much easier than phasing out CO₂ emission would be."

160

"How much CO₂ emission is too much?"

"> 2˚ C "is warmer than the Earth has been in several million years"

sea-level of half a meter "would seem to leave us on relatively safe ground, at least for the coming century."

160

"a 10-meter rise in sea level would displace 10% of humanity." 720 million people

161

"there are times in the past when sea level rose by several meters in century time scales."

"difficult to point a definite CO₂concentration that would be 'safe' from provoking to much sea level rise."

161

formula for ∆T_2x for CO₂concentration in the air = 2.5 - 4˚C or 3˚C

161-162

By not considering what happens after 2100 we can emit 2/3 more CO₂ than otherwise!

162

"For the coming decades, one simple way of looking at the situation is that the natural world is taking up CO₂ about half as quickly as we are releasing it."

163

"If emissions were cut by about half then the natural world would keep up with emission and CO₂concentration in the atmosphere would stop rising, at least for a while."

163

"cutting by half doesn’t seem attainable."

"Cutting U.S. emissions by half without sacrificing standard of living is doable."

163

"To reach that rate of carbon emission would require cuts in the developed world of about 80%. For the United States, Canada and Australia, the cuts would be closer to 90%."

163

"the 450 ppm stabilization scenario" cutting emissions by half will not do!

"Avoiding dangerous climate change requires emission cuts of around 80% by the year 2050."

164

2007 IPCC Mitigation Report calls for a "portfolio of solutions"

"while almost everyone else calls them wedges" after Pacala and Socolow

business as usual is BAU

BAU = 700 ppm or from 7 Gtons C per annum to 15 Gtons of C/ annum

164

420 ppm stabilization scenario

wedges

a doubling of fuel efficiency in cars from 30 to 60 m/g is for example a wedge