Per Wikipedia:
A change of 1.0-5.7 degrees C is a change of 1.8-10.26 degrees F. Cans someone explain why this is such a big deal? So Minneapolis in January is only -5 F instead of -15 – I’m sure Minnesotans can cope with this change.
Lots of things change with small changes in average temperature. I’m sure others have more expertise, but off the top of my head: Ice caps melt. Coastal flooding. Hurricanes more severe. Droughts. Forest fires worse. Crops fail.
The short answer is that global temperatures are remarkably stable over medium timescales (centuries and even millennia). Under natural conditions the earth’s energy budget from solar insolation is remarkably constant. When they do change much more rapidly than normal due to what climate scientists call “forcing”, such as warming driven by higher concentrations of greenhouse gases in the atmosphere, at least three different serious things happen.
One, the small changes are greatly amplified in specific regions, notably the Arctic, causing not only sea level rise but also a reduced albedo, meaning the land and sea gets darker from loss of ice cover and accelerates warming even further.
Second, rapid global temperature change leads to destabilization of the global climate by changing major atmospheric and oceanic circulation systems, such as the Atlantic Meridional Overturning CIrculation (AMOC), leading to potentially disastrous regional climate changes including some of the things @Procrustus mentioned above, and notably including generally more severe and unusual weather. Once-in-a-century extreme weather events potentially start to become more frequent, even annual events.
Third, and closely related, is that even small changes in average ocean temperatures, both deep and sea surface, lead to drastic risks to ocean life and corals, and to ocean acidification, and furthermore ultimately becomes a feedback in that oceans have been major mitigators of CO2 emissions by absorbing large quantities of it, but the warmer they get, the less they can absorb.
Some of these factors can lead to climate “tipping points”, where climate change becomes an uncontrollable runaway force due to the dominance of feedbacks.
Others are providing more detailed responses, but let’s boil it down to something easier to conceptualize:
The average January temperature in Greenland is 24-26° F. What happens to ice sheets and glaciers when you raise that average to 26-36° F?
Countries like Bangladesh will suffer from flooding. (Stockton, Calif is even lower at 13 feet above sea level. Bangkok’s average elevation is five feet.)
As your example of Minnesota implies, some useful habitats will be replaced with comparable habitats farther north. But the rain forests of Brazil and Central Africa will be dessicated but not replaced. Given high human populations and complex economies, ecological damage will pose difficulties. And of course the replacement of high-quality USA terrain with high-quality terrain in Canada will have economic and political consequences.
Th oceans will suffer not only rising temperatures, but rising acidity. Ocean ecosystems are already enduring rapid changes (although man-made disruptions unrelated to CO2 play major roles): Jellyfish are already dominant in some parts of the ocean recently dominated by fish.
Rapid changes will be disruptive economically even when the change isn’t obviously for the worse.
One example from when I was studying, so this is memory only. The lapse rate is the cooling of temperature as you increase elevation. A change of a few degrees can shift the normal snowline dramatically up or down a mountainside by hundreds of metres. Perhaps not a biggie on your Nepal postcard, but the consequences of such a change can be meaningful:
- total snowfall change determines how much the river that people rely upon receives
- change in the area of reflective snow cover changes atmospheric conditions, which have their own climatic effects for winds, storms and so on
- changes in vegetation cover, commercial opportunities, etc. on the mountainside
Se level rise is already mentioned in other posts. In coastal areas and ports, there is usually one day every 1-5-10 years where a combination of a storm surge, king tides and lots of rain causes localised flooding and a few days of mayhem. That is because all infrastructure is built to a certain height above sea-level, and usually not much more. A substantial increase in sea-level height - maybe as little as 10 cm - would increase the frequency of over-topping and localised flooding in your commercial ports significantly.
Because the starter numbers for climate change are so small and seemingly inconsequential, recent climate impact reports are being reframed to better convey things like the number of stinking hot days going from 1-2 per annum to 5-10. That makes it a bit easier to get your head around it.
A few points of clarification:
The “change” described is the surface global mean temperature anomaly. (Temperature anomaly in this case means a difference in trend as compared to either the pre-industrial baseline of 1850-1900, or relative to the 1950 baseline; different studies and assessments use different baselines and it is important to clarify what baseline is being used because they provide different reference values.) This represents an average temperature anomaly in measurements all over the Earth’s surface for some period of time (usually, unless it is being charted by month it is assume to be averaged over a 12 month period.) The mean, of course, doesn’t tell you anything about the variability; it is possible for the mean in a sample to not change but the variance to change radically, i.e. large temperature oscillations about the mean. There will also be variations in how much change is observed at different latitudes and climate zones; for instance, the temperature anomaly in the Arctic Circle is evaluated as three to four times greater than the mean, which has significant impacts on the accumulation of icepack and the resulting albedo of the Earth in reflecting sunlight. In other places the temperature anomaly may be much lower, but that doesn’t mean that they aren’t impacted by heating, just that they won’t experience the same extremes.
It should be understood that temperature anomaly, in this case, is being used as a proxy for additional thermal energy that is retained by the Earth instead of being radiated back to space due to the insulating effect of carbon dioxide, methane, and other greenhouse gases (GHG) in the atmosphere. (Although this is termed the “greenhouse effect” it doesn’t work in exactly the same way as glass in a literal greenhouse but the metaphor is good enough for nontechnical explanation.) We use temperature anomaly because it is something that can be derived more-or-less directly from measurement but if you add up what an additional +1.5 °C of the Paris Climate Accords threshold actually means in terms of the energy in the surface layer across the planet, it is actually a huge amount of additional energy.
Worse, it doesn’t actually represent all of the extra energy being absorbed. The oceans, which cover approximately 7/10ths of the Earth’s surface and have a much higher heat capacity, are darker and typically colder than the surrounding air, so they absorb incoming solar radiation far more efficiently than terrestrial terrain, and about 93% of excess heat is stored in the oceans. Because they are more dense and can also transfer heat into deeper layers of the ocean, the surface temperature of oceans rises much more slowly, causing them to act as a latent heat sink that is not visible from surface measurements. This means that even if all of the extra greenhouse gas were magically removed and we returned to an atmospheric GHG concentration of the pre-industrial baseline, we would still have extra heat being rejected back out of the oceans for a decade or more.
But wait, there’s more!. Aside from what happens on land and to the cryosphere (permanent and seasonal glaciers and snowpack), changes to oceanic heat distribution from excess heating cause changes to ocean main circulating currents (like the Atlantic Meridional Overturning Circulation that keeps Northern and Western Europe much warmer than it otherwise would be) which in large measure drive the weather patterns and regional climate behavior, and additional heat at the surface layer helps amplify tropical storms into more powerful, longer-lasting, and unexpected amplification of typhoons and hurricanes, as well as creating powerful moisture vapor conduits (‘atmospheric rivers’) which can result in massive weather systems that can deluge areas that are thousands of miles inland and drive tornadoes to much greater destructiveness and duration. It can also draw water away from areas resulting in desertification of previously arable regions.
So, the effects of global heating aren’t just a slightly greater variation in temperature; it also causes massive shifts in weather patterns, permanent (in terms of human timelines) changes in climate systems, a rise in sea levels threatening the nearly half of the population that lives with 100 kilometers of the ocean, often in low-laying areas, the loss of stabilizing mechanisms of the cryosphere and ocean circulating currents, causes the atmosphere to carry more water vapor (and thus, more momentum), and drives storms all over the world to be more powerful and prone to extreme rainfall and turbulence.
By the way, the IPCC reports are a ‘consensus’ view of climate change which includes the desire of non-technical policymakers to hew toward the less ‘scary’ predictions. Most scientists working in climate modeling and related fields consider the estimates of both temperature anomaly trends and effects to be under-predicted even notwithstanding the impact of climate tipping points (saddle points in climate-moderating mechanisms that, once achieved, will result in a new stability regimes that may have wildly different climate behavior and weather patterns). The reality is that we have already summited the +1.5 °C Paris threshold broadly considered to be the point at which dramatic and potentially irreversible changes to the climate system start to occur, and despite the progressively faster adoption of near-zero emission renewable energy technologies our collective atmospheric carbon dioxide and methane emissions continue to hit record highs, so we are on target to hit +2.0 °C sometime before 2050 (according to some projections, potentially before 2040), and almost certainly +3.5 °C to +4.0 °C by end of century (even assuming an inevitable curtailing of emissions as we just run out of accessible fossil fuels and either electrify or deindustrialize), which would be catastrophic for modern industrial society.
I am not an expert in climate science I have spent about the last fifteen years becoming conversant with the methods, tools, and assumptions underlying modern climate simulation and measurement as well as catastrophic risk assessment and what has come to be termed ‘attribution science’ (in essence, distinguishing between weather impacts that are a result of additional climate heating versus normal variability), including building simplified climate models and taking a critical look at measurements and assumptions. I actually started doing this because I was somewhat dubious about the confidence of predictions of dire outcomes for seemingly ‘moderate’ heating, and instead have come around to the position that most of the actual experts in various areas (especially marine hydrodynamics and cryosphere scientists) that we are actually on the cusp of––or have already committed the planet to––radical changes in Earth’s climate that pose a potentially existential threat to industrial society and potentially even to humanity at large. I’ve tried to avoid just giving a firehose of information here but I’m happy to do into more depth on specifics of particular areas or mechanism, or at least point to the appropriate resources to get more information.
Here is a good place to start on the impact of changes in Earth’s radiant energy balance:
Stranger
Even quite minor changes can have unexpected consequences when you’re dealing with natural systems in combination with human needs. We still rely on the natural world to work predictably for our food.
As an example, potatoes are commercially grown clonally, so you can save your small (‘seed’) potatoes and replant. Except, farmers don’t actually do this- they buy in seed potatoes every year. Part of the reason for this is potato plants gradually accumulate viruses, which pass to the tubers and keep multiplying, so plants get weaker and weaker the longer you replant from the same line. As well as passing from plant-tuber-plant, viruses are transferred between plants by aphids, so we grow virus-free seed potatoes in areas where the winters are cold enough that the aphids can’t live there.
Except… the winters are getting milder and now the aphids are starting to spread into the areas we’ve been considering as safe for decades. You might think it wouldn’t be too hard to just move production elsewhere, but there’s actually not much land well suited for seed potato production anyway, as it needs the right soil, suitable daylength and needs to be free of other spreadable pests and diseases, and we’re losing it. This is going to cause major problems in the UK in the near future if it carries on, and the only solution will be to start buying in seed potatoes. This is currently banned because everywhere we could import them from has diseases found there that we don’t currently have… and who knows how long their suitable areas will stay that way anyway.
This is just one crop, and one group of pathogens- but this sort of thing is happening all over global agricultural lands, all at the same time, all needing solutions, and all likely to get worse. The way things have worked since modern farming began are going to stop working. Things get a little warmer, plants start growing or flowering at the wrong times, pests and diseases on crops get worse and there’s no solutions that aren’t going to cause other problems, or that are going to work for very long anyway, and the problems are changing faster than we can find solutions.
And, of course, this is happening at the same time that people are going to have to deal with more extreme droughts and floods and areas of what was farmland becoming useless…
Even if Minneapolis wasn’t impacted itself, is it self-sufficient in food?
From the standpoint of Minnesota agriculture, an increase in winter lows from -15F to -5F would allow survival of more crop pests, threatening farm yields.
Less farm revenue means less state government tax revenue, diminished services…
Have the responses made sense and cleared this up for you?
Sure, if there were a nice even warming of, say, 10f (6c) all over the world AND it stopped there in 2100, it wouldn’t be too bad and quite manageable.
But in parts of Antarctica now it is 30c warmer than it should be! The effects vary wildly across the world. And, that forecast is of the state in 2100 - on the current trajectory of inaction the warming does not magically stop on that date!
This is the difference 4.5 degrees makes:
Or, in more detail,
Even that would be a dramatic change. This is essentially what we are currently seeing in the Arctic which which is resulting in progressive loss of summer sea ice and the increasingly likelihood of an ice free Arctic Sea by 2030. Not only would this be catastrophic for the ecosystems that depend upon ice flows and freezing conditions but it would continue the thawing of permafrost that is already threatening the viability of native communities and contributing to the release of carbon dioxide and methane which is trapped in the frozen tundra, as well as reducing the cold season effects that control pests and pathogens described upthread. In more mid-latitudes it would result in vastly more moisture in the atmosphere as water vapor content goes up ~7% for every +1 ℃ of surface warming, so a +6 ℃ increase in temperature would be roughly 30% more water vapor than today, which translates into more energy and momentum in atmospheric rivers and storm systems, as well as disruption of the Atlantic meridional overturning circulation (AMOC) and more frequent and aggressive cycling of the El Niño-Southern Oscillation (ENSO) cycle. At +6 ℃ we would experience megastorms of destructive power beyond human experience as regular events, and ironically also droughts and desertification as existing hydrologic cycles are disrupted, with rainforests, grasslands, and wetlands drying out, no longer being effective carbon sinks, and contributing to further increases in atmospheric carbon through wildfires.
Our current society and in particular our systems of agriculture are dependent upon the relatively stable conditions going back to about 10,000 years. A shift of +6 ℃ (even if it were somehow evenly distributed) within the span of a century would require massive adaptation and result in billions of deaths from famine, inescapable weather events and storm surges, sea level rise which would massively impact tropical and subtropical island nations and communities in low-laying seashore areas, and release of pathogenic bacteria and viruses frozen in tundra as well as migration of tropical pathogens and animal vectors toward the poles.
We will almost certainly run out of accessible ‘fossil’ hydrocarbon fuels before 2100 and emission rates will at least trend downward (there is no indication that we’re going to stop extracting and burning them in the interim until it becomes fiscally infeasible, and our industrial system of animal agriculture, which is the other main source of methane emissions, won’t be curtailed as long as it is profitable) you are correct that the temperature trends will continue to rise as we tick past various tipping points of cyrosphere loss, degradation of carbon-absorbing rainforests and wetlands, and reemission of thermal energy from the oceans when they hit saturation values. The ostensible ‘worst case’ of RCP 8.5 has a mean temperature anomaly projection of 3.7±1.1 ℃ but there are valid projections that go up to +6 ℃ by 2100. We are more likely on the RCP6 pathway with an estimated 2.2 ℃ (with variation of 1.4 ℃ to 3.1 ℃) but will almost certainly hew to the higher end of that range if not exceed it due to cryosphere loss and resulting reduced albedo, not even accounting for any other tipping points. Most climate scientists doing atmospheric system modeling that I’ve talked to expect a mean temperature anomaly of somewhere between 2.5 ℃ to 4 ℃ by 2100 based upon the most recent and highest fidelity models, with many not ruling out a potential for a +6 ℃ world sometime in the next century.
Stranger
We’ve “run out of accessible fossil fuels” several times in the past century or so. In no case did we stop burning fossil fuels: We just started accessing new sources that were previously considered “inaccessible”.
Perhaps a few anecdotes are more illustrative.
Does anyone remember the sky turning orange across the eastern seaboard from fires in northwestern Canada? Happened twice in the last few years. Before that? This was a result of a coincidence of issues. Beetles that affected western Canadian pine forests used to be mostly killed off in winter. A lot of dead trees now. Climate disruption - unusual drought. Excessively hot temperatures that summer - a perfect storm. BTW, not just western Canada - there were fire problems across Canada, drought on the prairies, etc. Recall too at least two different years recently of major forest fire problems in Australia.
Speaking of storms… I saw posts about serious flooding in NYC. For the second time recently, not to mention hurricane Sandy a while ago. Maybe it’s because of modern media, but I don’t recall news about flooding in NYC from 30 or 40 years ago. The effects of heat picking up extra moisture is evident in floods recently in Texas and South Carolina.
When we saw caravans of people coming north to cross the Mexican border - one of the triggers was drought and crop failures back home, which seems to be more common these days. The same is said of the flood of migrants trying to cross the Mediterranean rom Africa into Europe. So already, secondary effects are coming home to roost. I worry especially about Africa, where the largest growth of global population is expected the next couple of decades, yet climate for agriculture is becoming more erratic.
The above-mentioned snow pack issues have resulted in a steady drop in the amount of water in the Colorado river, and the lake level (Lake Mead) behind the Hoover Dam. The situation with glaciers is evident if you travel the Ice Fields Parkway, from Jasper (badly burned in forest fire last year) to Banff. You can get an excursion up onto a glacier, but it has receded drastically in the last century, as has pretty much every glacier on the planet. One of the major sources of power that is not fossil fuel is hydro-electric power. Make river flows unreliable and it cuts into that.
Not to mention water supply. Both Cape Town and Tehran have recently talked about major water supply issues, not just because of population size, but mainly climate change.
Maybe it’s modern media making this sort of news more accessible, but there does seem to be a trend of climate issues.
Indeed, we have to remember that fossil fuels are essentially sequestered carbon from millions of years ago. If we burned most of the available fossil fuels – the most abundant of which is coal (which could be converted to more useful forms like oil) – then the carbon emissions would return us to the climate of the cretaceous period, from about 145 to 66 million years ago. And it would do so at reckless breakneck speed, causing unprecedented instability in the global climate system. We absolutely cannot depend on “running out” of fossil fuels. We have to take drastic action to develop new energy sources and leave all that carbon safely sequestered.
While technology has allowed for extraction of previous inaccessible petroleum deposits such as deepwater oil and gas reserves, hydraulic fractioning (‘fracking’) to extract petroleum from oil-containing shale formations, extraction of bitumen from tar sands via gas injection, horizontal drilling, and pressurized waterflooding, there are physical limits on how much usable energy can be extracted at any reasonable marginal cost level. There will always remain deposits of ‘fossil fuels’ (and we have many decades of known natural gas reserves that could be extracted at a sufficiently high marginal cost) but when the energy cost of extracting the fuel exceeds what it can actually provide, the only reason to justify it is to maintain the existing infrastructure by subsidizing extraction through using other sources of energy, and in fact that is already happening for offshore oil, where wave energy is being used to extract oil and gas which really isn’t cost effective otherwise. The fracking industry which fueled the cheap oil boom of the 2010s and helped to stave off ‘peak oil’ from depletion of accessible conventional sources is actually upside down now because the flood of sources drove prices down to the point that it is barely profitable to extract it, and then the COVID-19 pandemic caused temporary decline in oil demand that nearly collapsed the market and caused fracking operations to run at a loss, to a point that investment banks are now largely unwilling to loan money to build new oil and gas facilities, and development companies have had to turn to other sources or take out loans with onerous repayment to continue development on facilities that were already in development.
Coal, of course, is the poster boy for this kind of collapse; it was the original ‘fossil fuel’ that powered the Industrial Revolution, and people thought there would never be an end to ‘cheap coal’ because even when a rich seam became played out there were almost always other seams nearby. But as demand increased exponentially during the era of electrification and costs for longwall mining operations increased, the high quality anthracite coal accessible at a reasonable marginal cost for commercial heating has virtually disappeared from North America, and the costs of operating plants to burn bituminous and subbituminous coal have increased such that it just isn’t cost effective in the United States to burn lignite for electrical production even with mountaintop removal extraction. Although coal energy advocates bemoan ‘environmental regulation’ and ‘compliance costs’ as having killed the coal industry, the reality is that coal just became completely unprofitable, and even though the US still has large undeveloped coal seams nobody wants to throw money into extracting it. The same will eventually occur around the world and with other ‘fossil’ hydrocarbon energy resources just because they are limited resources.
Unfortunately, despite the development and precipitous cost reductions of renewable energy (and the lagging but still advancing energy storage to ameliorate the variability in solar and wind energy), there is just no reason to believe that we will stop extracting and combusting ‘fossil fuels’ until it becomes too expensive even at a high marginal cost. In the last few years we’ve had simultaneous highest deployment of renewables and record use of hydrocarbon energy and atmospheric carbon emissions. In part, this is because while renewables have become extremely cost favorable for electric energy generation, there are significant segments of the transportation and commercial industries either that cannot shift to electricity with existing technology or are unwilling to invest in developing electrified alternatives.
There is also just a growing demand for electricity that, despite the rapidity at which solar and onshore wind can be deployed, just can’t be covered by renewables at the necessary scale, and is exacerbated by energy to power data centers and ‘AI’ (LLM) training facilities. There is also the issue that renewables take a large physical footprint and people often don’t want windfarms in their backyard or are concerned about the impact of literally ocean wave power systems (not without justification), and almost nobody wants lithium-ion battery storage in their town due to the very real concern about massive fires producing toxic smoke. You can see the desperation in all of the backing that fusion energy startups are getting in hopes of having commercial fusion power production in the next couple of decades even though none of these companies have achieved even breakeven of plasma heating to theoretical power production much less have any practical path toward commercial electrical power generation or breeding tritium fuel in sufficient quantities to be self-sustaining. In the meantime, to fill ‘the gap’ big electrical energy consumers are turning to fossil fuels (mostly natural gas but also coal, diesel, and bunker fuel even at much higher operating costs) to provide the kind of continuous power that solar and wind do not.
I don’t expect we’re going to stop burning hydrocarbon fuels from ‘fossil’ reserves until they become way to expensive to extract, and then critical energy demand will turn to biofuels even though those are ultimately even less sustainable due to water and fertilizer demands and inevitable phosphorous and nitrogen runoff pollution. There is zero appetite by governments of major energy producing nations around the world to impose ‘true cost of carbon’ penalties or to do anything more than make unenforceable on-paper commitments to reduction in carbon emissions that don’t just involved offshoring that demand so that they can move it off of their balance sheets and onto those of disadvantaged nations which can’t afford to ‘go green’ and meet their development expectations.
We’ll be running at full speed on extraction until sources peak out (probably sometime in the 2050s) and hitting the RCP6 (now RCP7 ‘baseline’) scenario, and if we could develop cost-effective third generation hydrocarbon biofuels we might even have a chance at something like an RCP8.5 because there is no indication that anyone is willing to deindustrialize or that per capita energy demand is going to voluntarily reduce despite projected global degrowth. And all of the ecologically-minded ‘liberal’ billionaires who have backed decarbonization are going to walk away from their previous positions as the cost to their own interests of doing so become apparent.
We’re pretty fucked, and we’re just going to get fucked even harder despite the projections that climate scientists have warned about for decades becoming reality before our eyes.
Stranger
We had something similar in the San Francisco bay area a few years back during massive wildfires.
An argument of “we’ll stop extracting fossil fuels when it costs more energy than we’re getting from it” is not, in fact, reinforced by an example of us continuing to extract fossil fuels even when it costs more energy than we’re getting from it.
Well, it’s a good thing I didn’t say that, then.
Stranger