XKCD's "Climate Change Timeline" | See History's Impact

[jedishrfu]

XKCD made a really cool Climate Change timeline:

https://xkcd.com/1732/

which shows the effect humanity has had on it vs history.

 

[jedishrfu]

No one is interested in climate change since the singularity happened.

 

[Greg Bernhardt]

Nice comic. The scale of time is a really difficult thing for humans grasp.

 

[jedishrfu]

Especially the new administration but I digress,

 

[JR Jonsson]

Cool timeline. Scary comic. Let's continue whith netmeeting as a start.

 

[NTL2009]

Interesting chart. The book by Randall Munroe is great also: https://whatif.xkcd.com/book/#thebook

I have a question about this. It seems odd to me that something like a 3 C shift would be so traumatic. I looked here:

http://www.infoplease.com/ipa/a0762183.html

and two adjacent cities in the list have a > 6F delta average in each season:

City Average monthly temperature (°F)
Jan. April July Oct.

Asheville, N.C. 35.8 54.1 73.0 55.2
Atlanta, Ga. 42.7 61.6 80.0 62.8

So while Atlanta is certainly hotter ( Hot'Lanta) than Asheville, neither is uninhabitable or traumatically different.I might call Atlanta a relatively hot climate, and Asheville a relatively mild climate. But neither is so extreme.

Yes, there is sea level rise, and other effects, but is a 3 C rise so awful? I'm not trying to 'argue' climate change, I am just curious about this specifically.

 

[Evo]

If we're going to actually discuss CC, we have to abide by the rules.

 

[NTL2009]

If we're going to actually discuss CC, we have to abide by the rules.

OK, thanks. I'm not sure what rules apply specifically. Were you addressing my post, or the thread itself?

 

[Evo]

OK, thanks. I'm not sure what rules apply specifically. Were you addressing my post, or the thread itself?

The thread. The rules are pinned above. https://www.physicsforums.com/threads/climate-change-global-warming-policy.757267/

I just wanted to make sure that the thread was in the right place before anyone responded to your question. You haven't done anything wrong.

 

[DrClaude]

Yes, there is sea level rise, and other effects, but is a 3 C rise so awful? I'm not trying to 'argue' climate change, I am just curious about this specifically.

From the IPCC:

Future risks and impacts caused by a changing climate

Risk of climate-related impacts results from the interaction of climate-related hazards (including hazardous events and trends) with the vulnerability and exposure of human and natural systems, including their ability to adapt. Rising rates and magnitudes of warming and other changes in the climate system, accompanied by ocean acidification, increase the risk of severe, pervasive and in some cases irreversible detrimental impacts. Some risks are particularly relevant for individual regions (Figure SPM.8), while others are global. The overall risks of future climate change impacts can be reduced by limiting the rate and magnitude of climate change, including ocean acidification. The precise levels of climate change sufficient to trigger abrupt and irreversible change remain uncertain, but the risk associated with crossing such thresholds increases with rising temperature (medium confidence). For risk assessment, it is important to evaluate the widest possible range of impacts, including low-probability outcomes with large consequences. {1.5, 2.3, 2.4, 3.3, Box Introduction.1, Box 2.3, Box 2.4}

A large fraction of species faces increased extinction risk due to climate change during and beyond the 21st century, especially as climate change interacts with other stressors (high confidence). Most plant species cannot naturally shift their geographical ranges sufficiently fast to keep up with current and high projected rates of climate change in most landscapes; most small mammals and freshwater molluscs will not be able to keep up at the rates projected under RCP4.5 and above in at landscapes in this century (high confidence). Future risk is indicated to be high by the observation that natural global climate change at rates lower than current anthropogenic climate change caused signi can't ecosystem shifts and species extinctions during the past millions of years. Marine organisms will face progressively lower oxygen levels and high rates and magnitudes of ocean acidi cation (high confidence), with associated risks exacerbated by rising ocean temperature extremes (medium confidence). Coral reefs and polar ecosystems are highly vulnerable. Coastal systems and low-lying areas are at risk from sea level rise, which will continue for centuries even if the global mean temperature is stabilized (high confidence). {2.3, 2.4, Figure 2.5}

Climate change is projected to undermine food security (Figure SPM.9). Due to projected climate change by the mid-21st century and beyond, global marine species redistribution and marine biodiversity reduction in sensitive regions will challenge the sustained provision of sheries productivity and other ecosystem services (high confidence). For wheat, rice and maize in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late 20th century levels, although individual locations may benefit (medium confidence). Global temperature increases of ~4°C or more¹³ above late 20th century levels, combined with increasing food demand, would pose large risks to food security globally (high confidence). Climate change is projected to reduce renewable surface water and groundwater resources in most dry subtropical regions (robust evidence, high agreement), intensifying competition for water among sectors (limited evidence, medium agreement). {2.3.1, 2.3.2}

 

[russ_watters]

Yes, there is sea level rise, and other effects, but is a 3 C rise so awful?

"Awful" is a value judgement and a matter of opinion.

 

[NTL2009]

The thread. The rules are pinned above. https://www.physicsforums.com/threads/climate-change-global-warming-policy.757267/

I just wanted to make sure that the thread was in the right place before anyone responded to your question. You haven't done anything wrong.

Ok, thanks. Ahhh, that pinned topic wasn't obvious to me, as I came here from the "New Posts" page - that takes me directly to the thread, and and the pinned posts are not visible unless you back up to that sub-forum listing.

I understand the 'hot button' nature of the topic, and I'm not interested in going there. I will try to word my posts carefully to avoid even the perception of approaching that line. Wish me luck! :)

 

[NTL2009]

"Awful" is a value judgement and a matter of opinion.

OK, you are right. This isn't easy! :)

So let me try this way - It seems that a temperature shift of ~ 3C would result in Asheville, NC having temperatures similar to what Atlanta, GA has today. Atlanta is a thriving city, and while they use a lot of A/C, life goes on each and every day, and I assume that Asheville would adapt over the time frame that is being estimated.

I can understand a much higher level of problems for those in/near very hot climates now. Some of those places are barely inhabitable now, so even a seemingly small shift in a fragile eco-system could push things past a breaking point.

I haven't looked at the IPCC reports in any detail for a few years now. I may try to do some digging again to better understand how they adjust for any positive, offsetting effects (longer growing seasons in cold regions, etc). But I guess that is separate from my earlier post, wondering if these changes are really so extreme for people in fairly moderate climates.

 

[jedishrfu]

... Wish me luck! :)

or "Reap the Whirlwind" from the movie "The Rock" thought it made sense to add a little weather humor.

 

[mfb]

@NTL2009: The main problem is not the temperature itself (a bit more AC does the job), the problem is the associated change in the weather.
http://www.nature.com/nclimate/journal/v3/n9/full/nclimate1911.html (in most regions), more droughts, more wildfires, ...
Most habitats shift a bit north (south in the southern hemisphere), which is not that problematic on its own, but it can make ecosystems less stable if the change happens too rapidly, and some ecosystems will stop existing because they cannot shift (limited to an island/river/...).

 

[mheslep]

@NTL2009: The main problem is not the temperature itself (a bit more AC does the job), the problem is the associated change in the weather.
http://www.nature.com/nclimate/journal/v3/n9/full/nclimate1911.html (in most regions), more droughts, more wildfires, ...

Yes, that's the theory per the models, but so far, per IPCC AR5:

“In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale"

“In summary, the current assessment concludes that there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness (lack of rainfall) since the middle of the 20th century due to lack of direct observations, geographical inconsistencies in the trends, and dependencies of inferred trends on the index choice. Based on updated studies, AR4 conclusions regarding global increasing trends in drought since the 1970s were probably overstated. However, it is likely that the frequency and intensity of drought has increased in the Mediterranean and West Africa and decreased in central North America and north-west Australia since 1950"

“In summary, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low”

 

[BillTre]

There are several things that concern me about climate change:

1) Species loss: some species will be able to move (or their offspring will) fast enough to keep from going extinct, but some won't; those that are on isolated mountains, for example, will only be able to go up to reach areas matching their temperature range. When they reach the top, they will run out of options. Species in the arctic can't move farther north. Things like polar bears and the nalwhal might well go extinct.

2) Ocean acidification: as there is more CO2 in the atmosphere, more of it will dissolve in the oceans and make them more acidic. This raises a lot of concern about pteropods in the ocean whose shell can be dissolved by these pH changes. Pteropods are at the base of the food pyramid for a lot of marine fish. Perhaps, if they died out, they might be replaced by some other zooplankton, but that is not now known, and if they were not replaced, ocean fisheries could well be decimated. pH changes such as these could affect other ocean organisms with calcium carbonate shells.

3) Ecosystem disruption in general due to loss of species. Species are now being lost a high rates (not all directly due to climate change, but to other human interventions like habitat destruction and spreading of diseases), similar to or exceeding rates seem in geology during major species extinctions. As species are lost, ecosystems become less stable and less productive.

 

[jedishrfu]

I wonder how the deep ocean currents will be affected if the Antarctic isn't freezing enough ice to make the brine river that drives the deep ocean current.

https://en.m.wikipedia.org/wiki/Thermohaline_circulation

 

[Davy_Crockett]

Thank you XKCD for the fun Climate Change timeline.

"No one is interested in climate change since the singularity happened."
This sounds so interesting. What on Earth does it mean?@NTL2009

I suggest observing averaged temp anomalies at:

http://cci-reanalyzer.org/wx/DailySummary/#T2_anom

and then observing the associated local temps at your weather website

(+0.5 average over 1979-2000 baseline may correlate with +5.0 local swing)

 

[NTL2009]

Thank you XKCD for the fun Climate Change timeline.

"No one is interested in climate change since the singularity happened."
This sounds so interesting. What on Earth does it mean?@NTL2009

I suggest observing averaged temp anomalies at:

http://cci-reanalyzer.org/wx/DailySummary/#T2_anom

and then observing the associated local temps at your weather website

(+0.5 average over 1979-2000 baseline may correlate with +5.0 local swing)

Interesting chart - but am I reading it correctly? It looks like it is displaying today's temperature versus average? If so, that is interesting, but isn't it more like "weather" than "climate"?

 

[Davy_Crockett]

"It seems odd to me that something like a 3 C shift would be so traumatic... is a 3 C rise so awful? ...I am just curious about this specifically."

...Why are you curious about this number specifically?

 

[Davy_Crockett]

To approach this topic one must first be familiar with the IPCC findings. IPCC is the gold standard. When you take time to digest and dig into these results and the process, you will know why. If you have any gut-willies, you will need to tamp these down and begin.

Since we are amateur enthusiasts we begin with a Summary and Synthesis paper:

https://www.ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf

Take your time reading and understanding this paper from beginning to end. It is do-able. More importantly, it is required if one plans to throw opinions around.

Yes, this updated report released every number of years generates a delayed perspective. The current release, AR5 from 2014 represents the scientific analysis and synthesis of evidence gathered prior to about 2010.

It is the research since 2010, which is in the process of being vetted and synthesized, that should be directed to in these forums and debated, not only as to methodology, but also as to implications.

 

[RogueOne]

I think it is good to discuss this topic. I would consider 20k years to be a very small sample of time in terms of a planet's lifecycle. Also, the climate data from the past is not as high-resolution as data of the present. What you see from the past is an averaged temperature over a span of centuries (maybe decades, at best, if something drastic enough happened in an area). You don't see the standard deviations in temperature for the past. What you see today when looking at the climate of the past decades/century, is data points from the average of a few months, so those deviations are not smoothed out. Those deviations are now visible. Any and all deviations/anomalies are going to look like abrupt and drastic changes to a person who cannot discern. They are using vastly different methods of measurement at drastically higher resolution than we can use to measure temperature retroactively. Have we even established what an acceptable standard deviation from the mean is? Have we established what the mean should even be? Do we know how axial tilt affects which hemisphere is exposed to more solar energy? (yes we do). Does combination of matter on the surface of the northern hemisphere have the same average specific heat as the matter composing the southern hemisphere? (Not even close). Why is the narrative fixating on CO2? We are closer to the lower limit of atmospheric CO2 needed to sustain carbon-based-life on Earth than we are to the maximum (We've actually had atmospheric CO2 reach 8,000ppm during ice ages).

I have read the IPCC articles, and my main concern is the fact that they use very short frames of reference to establish the lambda of certain parameters. They also do not look at climate retroactively more than a few thousand years. I feel that establishing an idea of a climate trend requires us to look at more long-term trends than that. 20,000 years is a microsecond in Earth's lifecycle.

A changing climate does exist, always has existed, and always will exist on earth. I think that a lot of people lose their cool on this topic (no pun intended). It is hard to find the direct line of communication between the opposing viewpoints because this field of science has been so politicized.

[Moderator's note: deleted off topic comments and unsourced image.]

 

[PeterDonis]

Thread closed for moderation.

Edit: Thread has been reopened. Please bear in mind the PF rules on the topic of climate change.

 

[DrClaude]

Why is the narrative fixating on CO2?

Because this is the main driver of the current climate change, as humans have transformed tons of carbon that was underground for millions of years into atmospheric CO₂.

We are closer to the lower limit of atmospheric CO2 needed to sustain carbon-based-life on Earth than we are to the maximum (We've actually had atmospheric CO2 reach 8,000ppm during ice ages).

I would really like to see a reference for that first statement. Also, nobody serious thinks that climate change will wipe out all life. It is the possible strong disruption of current life (including humans) that is worrying.

 

[mfb]

You don't see the standard deviations in temperature for the past.

You don't see them in the long-term temperature plots, but that doesn't mean the climate could have fluctuated wildly. Large fluctuations for decades lead to things that can be studied. As an example, currently many glaciers are melting at a rapid rate. The ice is gone forever - a new glacier might arise in the future, but that won't have the old ice of the current glaciers. Species that go extinct based on a changing climate can be studied in the future.

We are closer to the lower limit of atmospheric CO2 needed to sustain carbon-based-life on Earth than we are to the maximum

That is correct, but I don't see the relevance. The upper limit does not correspond to an environment humans want to live in.

@DrClaude: CO2 concentrations were at thousands of ppm long ago (compilation of sources here), the upper limit is more than twice the current value, which makes the statement true independent of the precise lower value.
Most plants use a C₃ cycle, which needs at least 150 ppm. There is also a C₄ cycle which works at much lower concentrations. (source, page 14)

 

[RogueOne]

Before you continue on reading this post, please understand that I do know there is a forcing/feedback relationship that the carbonate silicate cycle has Earth's climate. What I'm here to say is that I've seen some oversimplifications and cherry-picked frames of reference that dis-inform people as to what can be expected of our climate. There should be discernment between causes of climate change, effects of climate change, and feedbacks from climate change.

For us to not be in an interglacial period right now would be a divergence from almost 500 thousand years of well-documented glacial/interglacial periods of approx 100k years each. Given that we are in an interglacial period, our climate conditions are within the standard deviation for the point in the interglacial period that we are scheduled to be in right now.Here are charts and links to some IPCC publications that are objective and focus on the patterns, relationships, and mechanisms between the carbonate-silicate cycle and the climate. Its good to look back at the long term climate patterns and establish a good frame of reference.

"Box 6.2: What Caused the Low Atmospheric Carbon Dioxide Concentrations During Glacial Times?
Ice core records show that atmospheric CO2 varied in the range of 180 to 300 ppm over the glacial-interglacial cycles of the last 650 kyr (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-6-3.html; Petit et al., 1999; Siegenthaler et al., 2005a). The quantitative and mechanistic explanation of these CO2 variations remains one of the major unsolved questions in climate research. Processes in the atmosphere, in the ocean, in marine sediments and on land, and the dynamics of sea ice and ice sheets must be considered. A number of hypotheses for the low glacial CO2 concentrations have emerged over the past 20 years, and a rich body of literature is available (Webb et al., 1997; Broecker and Henderson, 1998; Archer et al., 2000; Sigman and Boyle, 2000; Kohfeld et al., 2005). Many processes have been identified that could potentially regulate atmospheric CO2 on glacial-interglacial time scales. However, the existing proxy data with which to test hypotheses are relatively scarce, uncertain, and their interpretation is partly conflicting.

Most explanations propose changes in oceanic processes as the cause for low glacial CO2 concentrations. The ocean is by far the largest of the relatively fast-exchanging (<1 kyr) carbon reservoirs, and terrestrial changes cannot explain the low glacial values because terrestrial storage was also low at the Last Glacial Maximum (see http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html#6-4-1). On glacial-interglacial time scales, atmospheric CO2 is mainly governed by the interplay between ocean circulation, marine biological activity, ocean-sediment interactions, seawater carbonate chemistry and air-sea exchange. Upon dissolution in seawater, CO2 maintains an acid/base equilibrium with bicarbonate and carbonate ions that depends on the acid-titrating capacity of seawater (i.e., alkalinity). Atmospheric CO2 would be higher if the ocean lacked biological activity. CO2 is more soluble in colder than in warmer waters; therefore, changes in surface and deep ocean temperature have the potential to alter atmospheric CO2. Most hypotheses focus on the Southern Ocean, where large volume- fractions of the cold deep-water masses of the world ocean are currently formed, and large amounts of biological nutrients (phosphate and nitrate) upwelling to the surface remain unused. A strong argument for the importance of SH processes is the co-evolution of antarctic temperature and atmospheric CO2. " - http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html

"atmospheric CO2 follows temperature changes in Antarctica with a lag of some hundreds of years. Because the climate changes at the beginning and end of ice ages take several thousand years, most of these changes are affected by a positive CO2 feedback; that is, a small initial cooling due to the Milankovitch cycles is subsequently amplified as the CO2 concentration falls"

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-6-1.html

 

[mfb]

Where is your point?
All those natural processes are slow. "<1kyr" is called "fast" already, the ice ages are even slower. Those natural changes are completely different from the change we had in the last 100 years.

 

[PeterDonis]

All those natural processes are slow

I don't think that's true of ocean CO2 uptake. The paper linked below, for example, shows large annual variations in ocean CO2 content, indicating that transfers of large amounts in either direction can occur on that time scale:

http://onlinelibrary.wiley.com/doi/10.1029/2010JC006625/full

 

[mfb]

I'm not talking about seasonal changes. They happen within a year by definition, but they are cycles. Deviations from those cycles are slow.

 

[PeterDonis]

Deviations from those cycles are slow.

Slower than annual, yes. But there is still plenty of evidence that the key processes involved change significantly on time scales much shorter than 1 kyr. For example, the following papers all describe significant changes in primary CO2 production in the ocean due to biological processes on time scales of a few decades:

http://www.sciencedirect.com/science/article/pii/S0079661115000993

http://onlinelibrary.wiley.com/doi/10.1029/2010GB004026/full

https://www2.cgd.ucar.edu/sites/default/files/asp-colloquium/files/Chavez-Messie-etal-2011.pdf

http://onlinelibrary.wiley.com/doi/10.1029/2010GB004026/full

Also, rates of upwelling are known to vary significantly on decadal timescales (I don't have any links handy at the moment but can find some if desired).

 

[RogueOne]

Where is your point?
All those natural processes are slow. "<1kyr" is called "fast" already, the ice ages are even slower. Those natural changes are completely different from the change we had in the last 100 years.

Keeping in mind the idea that IPCC states about CO₂ levels lagging behind temperature changes by a couple hundred years, there are a few factors that are compounding right now:

• The timing of the end of the mini ice age (sometime around the 1800s, although I don't know of an exact consensus on its end date)
• The carbonic uptake and storage during the mini ice age created a reservoir that has been being released in the past 100 years
• The warming that occurred in recovery from the mini ice age (solar energy output increasing)
• The long-term interglacial warming patterns which indicate that the Earth is scheduled to encounter long term warming trends right now regardless of recovery from mini ice age.
• Feedbacks created by these affects.
• Anthropological contributions (This list is primarily concerned with natural forcing, but I included this one as a gesture of solidarity and acknowledgment. I am making no claims about the extent to which this does or does not impact the climate.)

We're also discussing a sample of data that is measured with more certainty and resolution than is attainable while measuring temperature retroactively to the last time Earth has been at this point in an interglacial cycle.

 

[PeterDonis]

Because this is the main driver of the current climate change

It might be more appropriate, given the PF rules on this specific topic, to say that the IPCC reports, and the scientific research they are based on, conclude that CO2 is the main driver of the current climate change. That way the source you are relying on is clear.

 

[Greg Bernhardt]

Ultimately this thread does not meet our guidelines for discussion. If there are tangent discussions left unresolved feel free to start a new thread using peer reviewed sources. Closing up. Thanks!