Why natural cycles only play small role in rate of global warming

https://www.carbonbrief.org/guest-post-why-natural-cycles-only-play-small-role-in-rate-of-global-warming

by okket • 7 years ago

79 46 7 years ago

This was an interesting article and the author has strong data. I would want to know about the Younger Dryas [1] period though. This is a warming period about 12,000 years ago when some of the most devastating geological events we know of happen. This includes the outburst floods of glaciers holding back bodies of water larger than Lake Erie (Lake Agassiz [2] for example) and a temperature differential in Greenland of 27 degrees Fahrenheit cooler compared to today.

Human being play a huge role in climate change, but I don’t want to also write off the absolute enormous shifts than can occur naturally. We need to take those just as seriously for our own security.

[1] https://en.wikipedia.org/wiki/Younger_Dryas

[2] https://www.dmr.nd.gov/ndgs/ndnotes/agassiz/

GorgeRonde• 7 years ago

It was almost certainly caused by one or multiple comet fragment impacts.

Sources: https://scholar.google.fr/scholar?as_ylo=2018&q=hiawatha+cra...

lenticular2• 7 years ago

No, speaking as a former glaciologist, that's not likely to be true. The parent poster is correct. Younger Dryas featured multiple advances and retreats, which is inconsistent with an impact. Multiple impact over many centuries just isn't that statistically likely, and we would see better evidence of it.

Instead, the most probably cause is freshwater pulses coming out of the melting Laurentide ice sheet changing circulation in the Atlantic. This is actually quite well supported.

Younger Dryas was also confined to the parts of the northern hemisphere, mainly in higher latitudes. A large enough impact to significantly alter climate would see the resulting particulates globally mix in the atmosphere, resulting in more uniform cooling.

Instead, the fact that it was confined to parts of the northern hemisphere also supports the freshwater pulse hypothesis, since it is only a change in the transport of heat from the tropics to the pole, not a change in total heat.

The fact that freshwater pulses from the Laurentide ice sheet caused so much cooling is actually a concern with climate change. It's possible that it could happen again with melting of the Greenland Ice Sheet, at least a weakened version of it (the Laurentide Ice Sheet dwarfed the GIS).

Roark66• 7 years ago

The headline of this post is bullshit. The author of the article doesn't prove "natural cycles" play small role. He claims that the data he analyses points to the conclusion one specific 60-70 year old cycle of oceanic origin has far less impact on climate than commonly accepted. He talks about one mechanism, there are plenty of other natural mechanisms that affect the climate in various ways.

Quoting the article: >This means that ocean cycles on timescales of 60-70 years are unlikely to be a factor in the observed evolution of global temperatures since 1850. Instead, external factors, such as periods of strong volcanic activity and the release of aerosol particles (air pollution), have caused temperatures to fluctuate.

ocschwar• 7 years ago

There are other cycles, most of which are right now in a cooling phase, and yet we are warming. So those cycles (i.e. Milankovich cycles) can be written off already

Jill_the_Pill• 7 years ago

Or, rather than written off, treated as mitigating factors.

User23• 7 years ago

Plate tectonics are another huge factor. When Pangea existed there was just one ocean to distribute heat and no polar continent for glaciers to form on and increase the Earth’s albedo. That meant a much warmer planet.

The Quaternary glaciation is still ongoing because of those tectonic factors.

Another fun fact is that the warmest period in human existence was the Holocene maximum about 8000 years ago[1].

Geology is a fascinating field and thankfully lets us look at climate through a lens that isn’t intensely politicized.

[1] https://en.m.wikipedia.org/wiki/Holocene_climatic_optimum#/m...

inflatableDodo4• 7 years ago

If you look to the paper the article is about - 'A limited role for unforced internal variability in 20th century warming.' - it does seem to demonstrate that natural cycles play small role and the way it is set up it doesn't have to look at all natural cycles to do that.

Using a two-box impulse response model, we demonstrate that multidecadal ocean variability was unlikely to be the driver of observed changes in global mean surface temperature (GMST) after 1850 A.D. Instead, virtually all (97-98%) of the global low-frequency variability (> 30 years) can be explained by external forcing. We find similarly high percentages of explained variance for inter-hemispheric and land-ocean temperature evolution.

edit - link to paper - https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0555....

taneq3• 7 years ago

It still seems ass-about to me. The study doesn't show that natural cycles don't do much, it shows that in our models the external forcing they added is sufficient to cause the observed results.

We already know there's more going on than our models account for (consider the post-9/11 discovery of global dimming from airliner exhausts, as one example). There are probably a heap of effects pushing the measured temperatures in each direction that we don't yet know about.

(Note that I'm not saying natural cycles ARE responsible for the bulk of observed warming - just that this research doesn't seem to prove they're NOT.)

joe_the_user• 7 years ago

Yes, the headline is rather self-defeating. I studied persuasion techniques before the Internet got big and one of the trendy manipulation approaches then was to write an article titled "Why XXX" when XXX is some assertion you make, perhaps even with evidence but for which you don't actually offer an explanation (the reader never discovers why XXX, they are only that XXX is true, and why XXX is generally something people would be curious about). This technique naturally has become an arrow in the quiver of click-baiters but with click-bait sooo big now, using such bullshit is more likely to hurt a serious article than help it.

The proper title would be "we show human-generated carbon is sufficient to explain climate for the X many years", a significant claim by itself.

radford-neal• 7 years ago

From my initial glance at the post and paper, they seem to be claiming that the factors they do look at account for almost all the variation. If this is a correct attribution, then there can't be big role for any other factors, known or unknown.

Now, it's easy to fool oneself in this sort of modelling exercise - by fitting lots of parameters to the data, one can seem to account for lots of variation, without actually capturing the true relationship. I haven't looked at the paper in detail yet, so I can't say whether or not they avoided this pitfall.

apo• 7 years ago

The first graph ("External factors explain nearly all global temperature change") shows what appears to be temperature precisions of less than 0.1 degree C, yet reports no error bars.

How is it that a graph like this is even acceptable, given the importance of the conclusions? How does this study account for the inevitably poorer precision and accuracy of measurements made over 100 years ago? How are systematic errors (differences in measuring procedure, differences in time of day precision, etc.) accounted for?

A paper from Cowton/Way is available, but it appears to focus on filling in gaps from lack of data at the poles:

https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.22...

Where is the readily-accessible explanation for how the underlying dataset accounts for so many unknown factors?

jphenningsen• 7 years ago

Just from a first look, the caption of the figure references Figure 5 in Haustein et al 2019 [1]. You can see that this figure is way more detailed and includes a confidence interval. This article is clearly not a scientific publication but aimed at a broader audience. As for your other questions about the details of the methods used to gather and analyse this dataset, I am sure you can find plenty of information in the actual paper and references therein.

Generally speaking however let me comment that you will not be able to formulate a meaningful critique of the nitty gritty details you inquire about without the equivalent experience of at least a PhD in the specific subfield.

[1] https://sci-hub.tw/https://doi.org/10.1175/JCLI-D-18-0555.1

jolfdb• 7 years ago

"it's for a popular audience" is a bad justification for publishing misleading or wrong information that teaches people a wrong headed view of what a science is. It's not just poor quality, it's a actively harmful to culture and social progress. It's a supernormal stimulus, the journalism equivalent of replacing real foods by sugar and oil mixes -- it pushes people toward preferring wrong things over right things.

mikekij• 7 years ago

I'm so glad to see you bring this up. In my graduate physics training, I was taught to be extremely cautious about statistical significance, error propagation, and error bars. I remain skeptical of our conclusions about AGW, not because I have a political view on the subject, but because I'm skeptical that our temperature measurements from 120 years ago have a precision of less than 1 degree C.

But I (sincerely) assume that the climate scientists working in this space have compensated for this lack of precision in their conclusions. Right?

tasty_freeze2• 7 years ago

Hyperskepticism run wild. You, an outsider, doubt the science because you think that the people who have specialized in the field and have spent their careers collecting data are not as smart as you and have overlooked the quality of their data sets.

I'll go farther and say nobody better understands the limits of their data sets than the people who work with them.

jpeloquin• 7 years ago

Precision thermometry is an old science. Fahrenheit obtained a precision less than 1 °C using a mercury-in-glass thermometer in 1714. Platinum resistance thermometers were developed around 1900. These technologies are still used today.

Furthermore, accuracy greater than the precision of an individual measurement may be obtained by averaging multiple measurements.

All the tools needed to accurately track temperature existed 120 years ago. For what reasons do you believe that meteorologists did not use the tools available to them?

briantakita5• 7 years ago

This article's claims fail the smell test. Ultimately we don't know what we don't know & simplistic overarching models are probably missing key components, many of which are non-linear. 200 years is a tiny window when it comes to cosmological time. The methodology of measurement & extrapolation of data also needs public scrutiny. Interpretations of geological events are ridden with conjecture to fit an overarching narrative.

Here's what we have evidence of. Earth receives the majority of it's energy from the Sun. The Sun has significant fluctuations. Earth is affected not only by infrared & visible EM, but also by higher frequencies of EM. Earth is also affected by magnetism from the Sun. Earth's Magnetosphere is affected by the Heliosphere. A weaker Magnetosphere means less protection from Cosmic Rays, Coronal Holes, CMEs, & other space weather. Cosmic Rays perturbs water, seeds clouds, induces volcanic eruptions & earthquakes. Volcanic ash & cloud cover increase albedo, which cools the earth.

The "year without a summer" in 1816 (~200 years ago), was caused by the Mt. Tambora eruption. The Carrington Event happened in 1859.

briantakita5• 7 years ago

The climate is changing. The climate is being driven by the sun. Always has & always will. The climate is changing on other planets in the Solar system, being driven by the sun, just like Earth.

This whole "anthropocentric carbon climate change" scheme is a scam to funnel money away from real science & useful tech to special centralization interests that take away freedom of most people in the world. The people behind this scheme are a blight on humanity & should be arrested for fraud. The scale of their operations are orders of magnitude larger & more dangerous than Bernie Madoff.

dwaltrip• 7 years ago

It's not the sun: https://climate.nasa.gov/faq/14/is-the-sun-causing-global-wa...

briantakita5• 7 years ago

Except that model does not have accurate predictive qualities nor does it account for the other planets in the solar system going through climate change. What about Earth before humans? Here is a model that accurately predicts that solar cycle 24 would be weaker than cycle 23. Only 2 of 150 submitted models got that right.

https://www.researchgate.net/profile/Valentina_Zharkova/publ...

Another thing to consider as that a weakening Heliosphere & weakening Magnetosphere means Earth is more exposed to cosmic radiation. Cosmic radiation seeds clouds, excites water, drives earthquakes & volcanic eruptions. We may have an initial period of warming due to water being excited by cosmic radiation (similar to a microwave oven), but once enough volcanoes erupt, albedo will increase to offset the warming & cause cooling, as demonstrated by the Mt. Tambora eruption in 1816.

breakyerself3• 7 years ago

The planets been breaking temperature records like hotcakes while solar irradiance has been declining for decades. There is zero evidence for magnetosphere driven climate change. What you've written is just some sciencey sounding BS that rationalizes an irrational position.

briantakita5• 7 years ago

Except the records being broken are low temperature records. They aren't actually records in the geological sense, just measurement records in modern times. The "year without a summer" was colder for example.

The magnetosphere does not drive the climate. The magnetosphere protects Earth from space weather, which includes Cosmic radiation, Coronal holes, Coronal mass ejections, etc.

Are you seriously claiming that the sun has no effect on the climate? Are you claiming that the sun does not have cycles? And you call me irrational...

instantwhat• 7 years ago

If, tomorrow, NASA, NOAA, and the UN IPCC held a joint press conference to announce surprising new evidence which indicated that anthropogenic effects on the climate were minimal, that we could not noticeably affect the climate, regardless of our emissions, and that the climate was essentially out of our control, what would your reaction be? Would that be good news or bad news? Why?

yeahitslikethat• 7 years ago

Why do we continue to debate climate change focusing on centuries old data when the carbon cycle takes hundreds of millions of years? Any data we've collected amounts to less than a rounding error.

f00_• 7 years ago

Have been reading the late and great David MacKay's Sustainable Energy - Without the Hot Air lately (completely free on withouthotair.com)

https://www.withouthotair.com/c1/page_5.shtml

The climate-change motivation is argued in three steps: one: human fossil- fuel burning causes carbon dioxide concentrations to rise; two: carbon dioxide is a greenhouse gas; three: increasing the greenhouse effect in- creases average global temperatures (and has many other effects).
Fossil fuel burning increases CO2 concentrations signiﬁcantly. But does it matter? “Carbon is nature!”, the oilspinners remind us, “Carbon is life!” If CO2 had no harmful effects, then indeed carbon emissions would not matter.
However, carbon dioxide is a greenhouse gas. Not the strongest greenhouse gas, but a signiﬁcant one nonetheless. Put more of it in the atmosphere, and it does what greenhouse gases do: it absorbs infrared radiation (heat) heading out from the earth and reemits it in a random di- rection; the effect of this random redirection of the atmospheric heat trafﬁc is to impede the ﬂow of heat from the planet, just like a quilt. So carbon dioxide has a warming effect. This fact is based not on complex historical records of global temperatures but on the simple physical properties of CO2 molecules. Greenhouse gases are a quilt, and CO2 is one layer of the quilt.
One last thing about the climate-change motivation: while a range of human activities cause greenhouse-gas emissions, the biggest cause by far is energy use. Some people justify not doing anything about their energy use by excuses such as “methane from burping cows causes more warming than jet travel.” Yes, agricultural by-products contributed one eighth of greenhouse-gas emissions in the year 2000. But energy-use contributed three quarters (ﬁgure 1.9). The climate change problem is principally an energy problem.

Watched Merchants of Doubt recently, point that stuck with me most is that people against global warming are motivated by libertarianism, and anti-communism. lots of the contrarian scientists worked during the cold war. Will be checking out the book version soon

I don't think you even need the climate change motivation to get behind moving off fossil fuels (supply chain security is another huge one, I find climate change deniers often also in the peak oil camp). The way David MacKay presents the numbers allows people to come up with realistic plans to move off fossil fuels on their own instead of reciting someone else's dogma

Teasing out cause and effect is difficult especially with something that we can't perform randomized experiments on. I'd like to read more about counterfactuals and causal analysis of climate change

Judea Pearl has a great little bit about this in The Book of Why

Until recently, climate scientists have found it very difficult and awkward to answer questions like “Did global warming cause this storm [or this heat wave, or this drought]?” The conventional answer has been that individual weather events cannot be attributed to global climate change. Yet this answer seems rather evasive and may even contribute to public indifference about climate change.
Counterfactual analysis allows climate scientists to make much more precise and definite statements than before. It requires, however, a slight addition to our everyday vocabulary. It will be helpful to distinguish three different kinds of causation: necessary causation, sufficient causation, and necessary-and-sufficient causation.
Using these words, a climate scientist can say, “There is a 90 percent probability that man-made climate change was a necessary cause of this heat wave,” or “There is an 80 percent probability that climate change will be sufficient to produce a heat wave this strong at least once every 50 years.” The first sentence has to do with attribution: Who was responsible for the unusual heat? The second has to do with policy. It says that we had better prepare for such heat waves because they are likely to occur sooner or later. Either of these statements is more informative than shrugging our shoulders and saying nothing about the causes of individual weather events
Climate scientists can get counterfactuals very easily from their computer models: just enter in a new number for the carbon dioxide concentration and let the program run.

and one of my favorite quotes from MacKay:

Please don't get me wrong: I'm not trying to be pro-nuclear or anti-wind. I'm just pro-arithmetic

Why natural cycles only play small role in rate of global warming

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