Arguments
SkS Analogy 18 - Cliff jumping and temperature changes
Posted on 30 January 2019 by Evan, jg
Tag Line
Regardless the height of the cliff, jumping from cliffs is deadly.
Elevator Statement
Regardless of the height of a cliff, jumping from cliffs is deadly. Hang-gliding from cliffs thrills. Jumping from cliffs kills. Jumping 10 m from a cliff that is 1000 m above sea level hurts just as much as jumping 10 m from a cliff that is 900 m above sea level.
Increasing or decreasing the global average temperature causes sea level to rise or fall. Rapidly increasing or decreasing the global average temperature will likely cause sea level to rapidly rise or fall. It does not matter what the current global average temperature is. Causing the global average temperature to jump, as we are, causes sea level to jump. A snail can outrun sea level change, but houses, sky scrapers, buildings, subways, and roads move slower than snails. They sit where they are and drown. Are your children and grand children prepared for this coming future? Is there anything we can do to slow down the ongoing global temperature jump?
Climate Science
The motivation for this analogy is to explain why the science community focuses on "temperature anomalies" (i.e., temperature changes) instead of absolute temperatures. It does not matter what the Earth's temperature was before the start of the industrial revolution. It is the temperature change since then that is causing problems. The Paris Accord strives to limit global warming to no more than 2°C above pre-industrial levels, and does not specify a specific, absolute global average temperature that we need to stay below.1
If we were doing something to cool the Earth it would also be harmful, because cooling the Earth would cause sea level to fall, and likely would also shift precipitation patterns, agricultural zones, etc. It is not the absolute average temperature of Earth that matters. What matters is that we've spent about 7000 years settling 8 billion people around the Earth in just about every habitable nook and cranny with the climate to which we've become accustomed. Changing that climate by changing the temperature will have consequences.
Footnotes
1. Read here for more information about how and why 2°C became adopted as the upper limit of warming acceptable in agreements designed to limit warming.
The current interglacial period called the Holocene has had very stable temperatures (within 1 degree of variation) over about the last 10,000 years, and this perfectly suits agriculture, which appeared early during this period and flourished. Prior to that period during the ice age climate variation had huge global swings.
Agriculture loves a stable climate, and has been the foundation of advanced human civilisation. We are putting all this at risk. This guy is a chemistry teacher and has some really good thoughts on it.
According to the work of James Hansen et al climate sensitivity roughly follows a U-shaped curve, which means the further you get from your approximately stable start point the faster change occurs.
Hansen and Sato Estimate Climate Sensitivity from Earth's History
The longer we push this process the more dangerous it gets with major tipping points like the loss of polar ice sheet stability, ice albedo effect and altering of ocean and atmospheric circulation.
We're now experiencing in North America what a destabilized Arctic vortex means with very cold air that usually sits over the North Pole during winter being pulled deep into the continent producing record cold in many places.
We'll also see these extremes in coming years as ocean levels increase and record storm activity creates record storm surges. Not a possibility now, a statistical certainty given the conditions.
A safe level of CO2 is almost certainly below;
350 ppm
Doug C.:
While many mass media outlets have reported record cold, it has not yet been as cold as it used to be from 1900-1950.
At the NCDC temperature records page they currently record no monthly cold lows or monthly cold highs set in the past 7 days. I have seen several reports of daily records (not monthly or yearly records) that might be set tonight. It is possible that the data has not had time to be recorded yet, we should check back in a few days. Since it is January a yearly cold record would be unusual cold while a daily record is not as significant.
Cliff Mass has a post that shows cold spells are warming faster than average global warming (hat tip to snape at Tamino's).
Until the data shows a few all time lows the "record polar vortex" is so much smoke. A post at Tamino's showed that in Minneapolis the number of days per year -20F or lower has dramatically decreased for the past several decades. I heard a newsman report on PBS that it was the "coldest it had been in 50 years". Global warming really got going 50 years ago. A 50 year record would be a cold, but not exceptional day, in the 1920's.
During the "Summer in Wnter" in 2012, in at least 4 locations the low temperature at night was higher than the previous highest temperature ever recorded (at locations with long periods of record). Several daily records were broken by 30F. We will see if this cold spell actually sets any significant records next week.
The deniers like to hype average cold spells as record setting, don't believe them. If it is the coldest day in 20 years it is as cold as an average cold day 75 years ago.
The cold weather in America might well be nothing truly record setting, but there is some preliminary evidence climate change is altering the behaviour of the polar vortex, and leading to potentially lengthy and more frequent periods of very cold winter temperatures in America.
en.wikipedia.org/wiki/Polar_vortex#Climate_change
Nigelj,
Read the link to Cliff Mass. The data show that cold waves are much less frequent and are warmer than they used to be. They are warming faster than the global average.
If you look at the all time temperature records at the NCDC (linked above) in the past 365 days in the USA there were 181 hot records and only 5 cold records (!!!). That is because hot records are much more common than they used to be and cold records are much less common.
In the NCDC all time global records in the past 365 days there were 568 hot records and only 18 cold records. I do not know how many global sites they use. Many news reports call temperatures that are the coldest for the past 50 years a "record cold" even though it used to be much colder. I also heard "coldest in a generation" which is generally only 30 years. People forget what it used to be like.
I am sorry, in the USA there were 7 cold records in the past 365 days.
michael sweet @3
You're right to advise caution as weather extremes are often misrepresented as "proof" that a long term warming is not taking place.
It's important to note that global warming and climate change is a long term trend taking place over the entire globe. And while local cold weather records may be broken, this is almost certainly a result of the chaotic disruption of weather caused by a global transition to a warmer Earth.
In the case of some periods of cold weather in North America, this may be due to the fact that generaly warmer temperatures in the Arctic have disrupted atmospheric circulation that in the past has tended to isolate very cold air masses above the Arctic in the winter.
This can result in unusual weather across North America such as a few year ago when we in Edmonton Alberta were experiencing unusually mild weather well above freezing when Florida was seeing sub zero weather and snow.
Regarding America's current very cold weather: NOAA's Brilliant Response To Trumps Climate Tweet
I grew up in Minnesota, and winter was not winter until we had one or two weeks when daily highs were below 0 and lows were in the -20's or colder. Now we have a couple days when it's cold, and this weekend we will be in the higher 30's low 40's!
The last thing you need when standing on the edge of a cliff is a great leap forward.
nigelj
Ruddiman has a very plausable theory on why this interglacial has been so much more stable, climate wise, than previous interglacials. See Plows Plagues and Petroleum. A fascinating read.
nigelj@11 I think you are missing a link.
Evan @9
I grew up in north central British Columbia and in the late 1960s remember being kept home from school because the temperature had gone below -50F and there was concerns about frostbite in our young lungs.
In the 1980s working in the forestry sector there was one winter when it went below -40C and stayed there for a week. That was the last prolonged deep freeze I can remember here. We still get cold snaps but not like decades ago and the forests really show it. It takes prolonged deep cold to kill off large numbers of pine beetle who burrow into trees to lay eggs and produce natural antifreeze to make it through the winter.
All the dead trees covering BC are just one more sign of climate change to many of us.
Doug_C@13 Before I woke up to the reality of GW/CC about 7 years ago, before that time I started noticing what I called digital weather, where Spring would be wet and cold for about 2-3 months, then summer would be dry and hot for 2-3 months. In general Minnesota winters have been much milder than when I grew up. I remember experiencing -35F, but not -50F. In my generation (late 50's) I can't think of anyone I've talked with who does not remark about how winters are currently milder than in the 60's and 70's.
Here's another analogy, regarding climate action:
Suppose the map says you are driving toward a cliff, but Big Fossils in the back seat says the map was drawn by communists. You've been driving in the Southwest for hours and its been flat as a pancake, doesn't a canyon seem rather farfetched (even in a place called 'Canyonlands')? Anyways, at some point you see that there is a cliff up ahead so you jam on the brakes. So, here's the problem: you're driving an 18-wheeler loaded top to bottom with bricks. By the time you see the cliff, its too late. That loaded truck is the ocean. The step between 'global heating' (due to top-of-atmosphere radiative imbalance) and 'climate change' is 'ocean warming'. And by the time you feel the climate changing, the sheer thermal mass of the warmed ocean makes it almost impossible for any braking action to keep you from harm. You should have trusted the mapmakers. But as 'everyone knows' they are scientific hoaxters bent on global wealth redistribution, or something like that. So, off the cliff you go...
It appears that the NCDC temperature records page is down due to the government shutdown. My previous numbers were probably incorrect.
The NSIDC had this to say about the "record cold" during January:
"Conditions in the upper US Midwest were colder than any previous winter period in the past two decades. Low temperatures in northern Minnesota and all of Wisconsin on January 30 and 31 were in the -27 to -35 degrees Celsius range (-17 to -31 degrees Fahrenheit). Large areas of Michigan, Ohio, Indiana, Iowa, and the Dakotas reached temperatures below -20 degrees Celsius (-4 degrees Fahrenheit). However, few all-time low temperature records were set during the cold snap. Very mild [hot] conditions followed the cold snap in early February." My emphasis. source
Some "record cold", a few records and then warm weather. The deniers crow about normal cold and the mass media follow along. In the 1920's this would have been cold but not exceptional. People have forgotten what cold weather was. Cliff Mass was right.