Rise in world's temperatures accelerates

 Open Mind (Tamino) produced a previous piece about the acceleration in the rise in global temperatures, which I reported on here.  He has returned to the analysis, and confirms his position in his latest post. 

I now have global temperature data through October of this year from NASA, NOAA, and ERA5, as well as data through September from HadCRU and Berkeley. I’ve translated them to “since pre-industrial” values using one of the methods in the IPCC special report on 1.5°C. Then I computed yearly averages (this year is incomplete so values for 2024 are year-so-far averages)

There are two clear episodes in this plot: before and after 1975. Before, GMST was fluctuating but not trending either way; since, it has been trending consistenly up and fluctuating. As for its rate of increase, for four and a half decades (from 1975 until 2020) temperature seemed to rise at a pace (about 0.02°C per year) that was unchanging, and statistics couldn’t deny it.

But the last two years (2023 and 2024) have been “off the charts,” so to speak. For the data from ERA5, the value for 2024 year-so-far is already above 1.5°C, which is exactly what the Paris agreement seeks to avoid.

I investigated the rate of warming, and how it may have changed over time, in two ways. First, I fit a modified lowess smooth which I’ve programmed to estimate the rate as well as the value. Second, I computed a piecewise linear fit (PLF) with knots at 1975 and 2010. Both models (lowess and PLF) were fit to the monthly-average data, but in the graphs that follow I’ll plot yearly averages so the graphs will be less cluttered. Here’s how the PLF model fits the data from NASA:

PLF = piecewise linear fit 

 

[....]

For the 45-year period from 1975 through 2009, the average warming rate according to NASA data is just about 0.018°C/yr. For the 15-year period since 2010, it has been a lot faster at 0.031°C/yr. Statistically, the difference is significant at over 99% confidence.

I have also adjusted all the data sets, to compensate for the influence of el Niño, volcanic eruptions, and solar variations, with a method not unlike that of Foster & Rahmstorf (2011). Here are the adjusted temperatures, together with their PLF fit, for the data from NASA:

This chart shows the temperature anomaly adjusted for El Niño/La Niña and for vulcanism. 
PLF = piecewise least fit.

The rate from 1975 to 2010 now seems to be only 0.017°C/yr, and after 2010, the best estimate is 0.033°C/yr. These aren’t much different from the estimates using the raw data, although the uncertainties are now smaller so the confidence intervals are narrower.

Falling emissions (which of course we don't have--emissions continue to rise) do NOT mean that temperatures will start falling.  The RISE in the temperature anomaly is proportional to the LEVEL of emissions.  In other words, for temperatures to stop rising, we need to reduce emissions to zero.  If we halve emissions, the increase in temperature anomaly will halve, but that only reduces it to what it was before this recent acceleration, 0.17 degrees per decade.  

There are positive signs that emissions will peak soon.  Wind and solar continue to expand exponentially.  The costs of battery storage are plunging, and the recent first commercial solid-state battery points to continued and sustained cost declines and efficiency improvements.  Yet, even if we completely switch ALL electricity generation and ALL land transport to carbon-free methods, that will still only halve emissions.  If we were to start cutting emissions by 5% a year, compound, it would take us 40 years to reduce emissions to 10% of current levels.  Assuming we did this (but we are not) temperatures would rise for the next decade by 0.33 degrees, for the decade after by 0.17, by the decade after that by 0.l2 degrees and for the final decade by 0.06.  Roughly.  In other words, temperatures would rise by another 0.33+0.17+0.12+0.06, or ~0.7 degrees, making the rise since 1850-1900, the traditional "pre-industrial" starting point 2.2 degrees.

We face catastrophe, and still we dither and phaff.  The Right is dead against doing anything at all to slash emissions, and the Left argues with itself about what to do.  Meanwhile, we are lied to by corporations and governments, and protesters go to jail while oil execs are fêted.

A single volcano does not emit more than all mankind

 

Mt Cleveland, Alaska (Wikipedia Commons)

From Snopes

The myth that a single volcanic eruption puts more CO₂ into the atmosphere than all of mankind to date, let alone 10,000 times more, is one of the most pervasive as well as one of the most demonstrably false climatological claims out there. It stems, ultimately, from a geologist named Ian Rutherford Plimer, infamous for writing a widely discredited book titled Heaven and Earth, which attempted to argue that humans have had an insignificant effect on global climate. [Plimer is a well-known Australian climate denialist]

In a 2009 editorial written for Australia’s ABC news, he echoed a sentiment he had argued with similar inelegance in his book by providing the following statement, widely spread nearly word-for-word in climate skeptic circles, without any supporting citation: “Over the past 250 years, humans have added just one part of CO₂ in 10,000 to the atmosphere. One volcanic cough can do this in a day.”

This brief statement — a mere 28 words — yields a remarkably dense buffet of spurious claims and outright falsehoods. It also is rife with ambiguity. What numbers is he actually comparing? What is a volcanic “cough”? From a fact-checking standpoint, there are no interpretations of Plimer’s second sentence that can produce a factual assertion.

[....]

A more scientifically valid approach, perhaps, would be to compare annual volcanic emissions fluxes to annual anthropogenic fluxes, as the carbon cycle is an ever-shifting network of sources and sinks of CO₂ that need to be accounted for. A 2013 review attempted to estimate the annual contribution of CO₂ emitted from all volcanoes (active and passive) and other tectonic sources on Earth per year, coming up with a figure of 540 megatons per year (note that these measurements, unlike the ones above, represent the total mass of CO₂ not solely the carbon component):

[CO2 from the plumes of actively erupting volcanoes]:

Using the available data from plume measurements from 33 degassing volcanoes we determine a total CO2 flux of 59.7 Mt/yr. Extrapolating this to ~150 active volcanoes produces a total of 271 Mt/yr CO2.

[CO2 passively vented by active volcanoes]:

Extrapolation of the measured 6.4 Mt/yr of CO2 emitted from the flanks of 30 historically active volcanoes to all 550 historically active volcanoes produces a global emission rate of 117 Mt/yr.

[CO2 from other volcanic sources]:

Perez et al. (2011) calculated the global emission from volcanic lakes to be 94 Mt/yr CO2. The sum of these fluxes produces an updated estimate of the global subaerial volcanic CO2 flux of 474 Mt/yr. Emissions from tectonic, hydrothermal and inactive volcanic areas contribute a further 66 Mt/yr to this total […], producing a total subaerial volcanic emission of 540 Mt/yr.

While the authors of this study note that this is an exceedingly rough estimate, they also point out that it is orders of magnitude lower than estimates of the annual flux of CO₂ added to the atmosphere through human activity, currently estimated to be around 35,000 Mt/year:

The global subaerial CO2 flux we report is higher than previous estimates, but remains insignificant relative to anthropogenic emissions, which are two orders of magnitude greater at 35,000 Mt/yr. 

Once again, the actual numbers bear no resemblance to Plimer’s claims. It would have to be a pretty heavy volcanic “cough” from a “single volcano” to, by itself, increase Earth’s annual volcanic CO₂ flux by a factor of 65.

Absurdity notwithstanding, numerous online claims reference specific volcanic eruptions purported to have added more than the total emission of anthropogenic carbon ever released (a value, estimated above, to be more than 282 Gt of carbon). The most commonly cited are the 15 June 1991 eruption of Mt Pinatubo and the 18 May 1980 eruption of Mount St Helens. According to the United States Geological Survey (USGS), Mount St. Helens released 0.01 Gt to the atmosphere and Mount Pinatubo released 0.05 Gt. Put another way:

There is no question that very large volcanic eruptions can inject significant amounts of carbon dioxide into the atmosphere. The 1980 eruption of Mount St. Helens vented approximately 10 million tons of CO2 into the atmosphere in only 9 hours.

However, it currently takes humanity only 2.5 hours to put out the same amount. While large explosive eruptions like this are rare and only occur globally every 10 years or so, humanity’s emissions are ceaseless and increasing every year.

Temperatures have been rising for 100 years

 Global temperatures have been rising for over a hundred years, though the faster rise only began from the 1970s onwards.  This coincided with a steady expansion in CO2 and other greenhouse gas emissions, which accelerated after WW2 and again with the rise of China.   Note 1) the occasional random spikes up, and down; 2) cycles around the rising trend caused by such natural cycles as ENSO  (El Niño Southern Oscillation); 3) occasional 2-3 year blips caused by volcanic eruptions (for example after the Mt Pinatubo eruption in 1991).  

Temperatures have drifted lower since the last El Niño, in 2016, just as they did in the one before in 1998.  The post 1998 decline led many to conclude that global temperatures had stopped rising, though that notion was dispelled when the next ENSO cycle came along.  Over the next couple of years, the volcanic eruption in Tonga will likely cool the Earth by at least 0.5 degrees, because of the emission of sulphur dioxide aerosols.

(Chart from  Our World in Data)

Last 7 years hottest ever

 From NOAA

Source: NOAA

Cooler than it was in 2020, because it was a La Niña year.  A fair bit cooler than 2016, an El Niño year, when the Pacific gives up some of the heat it has absorbed during the La Niña.  Still, the last 7 years have been the warmest measured by thermometer in the last nearly 150 years, and, using numerous proxy measurements, the hottest in the last 2000.  Temperatures will drop over the next couple of years because of the massive eruption of the volcano in Tonga.  No doubt, denialists will have a field day, pointing out that temperatures have fallen since 2016.   After all, after the last big El Niño in 2008, they dined out for years on the fact that temperatures had "stopped rising", ignoring the ENSO  (El Niño- Southern Oscillation) cycles.

Global temps to fall by 0.5 degrees after Tonga eruption

From a video by Everything Science.   Ignoring the clickbait headline ("A new ice age?"), the conclusion, based on previous examples of massive volcanic eruptions, is that global temperatures could fall by ±0.5 degrees for a period of ± 5 years.  This is 25 years of rising global temperatures temporarily reversed in one single event. 

 More scientific analysis will no doubt come up with more reliable estimates over the next few months.  I'll keep you posted.

100% of global warming is due to humans

From Carbon Brief:

During a recent congressional hearing, Rick Perry, the US energy secretary, remarked that “to stand up and say that 100% of global warming is because of human activity, I think on its face, is just indefensible”.

However, the science on the human contribution to modern warming is quite clear. Humans emissions and activities have caused around 100% of the warming observed since 1950, according to the Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report.

Here Carbon Brief examines how each of the major factors affecting the Earth’s climate would influence temperatures in isolation – and how their combined effects almost perfectly predict long-term changes in the global temperature.

Carbon Brief’s analysis finds that:

• Since 1850, almost all the long-term warming can be explained by greenhouse gas emissions and other human activities.

• If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred. They are offset by cooling from human-produced atmospheric aerosols.

• Aerosols are projected to decline significantly by 2100, bringing total warming from all factors closer to warming from greenhouse gases alone.

• Natural variability in the Earth’s climate is unlikely to play a major role in long-term warming.

As is usual with Carbon Brief articles, they are well worth reading in full.  You can do that here.

Geo-engineering

I am optimistic that the falling costs of renewables and EVs and the rapid improvement in batteries will lead to significant declines in emissions over the next 20 or 25 years.  And if global temperatures continue to rise by 0.2 degrees C per decade (and don't accelerate), that will take us to the 1.5 degrees lower limit set in Paris.  However, even if emissions stop completely in 2040 (and they won't, even if they will be a lot lower than now) temperatures will go on rising after 2040 for another 30 or 40 years, by another 0.6 degrees.   This is because of the thermal capacity of the world's oceans. 

Is there anything we can do, apart from the obvious (roll out renewables even faster), to prevent that?

Mt Pinatubo eruption, 1991

The most "popular" potential solution is to mimic the effect of volcanoes.  Take the eruption of Mt Pinatubo in 1991:

The 1991 eruption of Pinatubo produced about 5 cubic kilometers of dacitic magma and may be the second largest volcanic eruption of the century. Eruption columns reached 40 kilometers in altitude and emplaced a giant umbrella cloud in the middle to lower stratosphere that injected about 17 megatons of SO2, slightly more than twice the amount yielded by the 1982 eruption of El Chichón, Mexico. The SO2 formed sulfate aerosols that produced the largest perturbation to the stratospheric aerosol layer since the eruption of Krakatau in 1883. The aerosol cloud spread rapidly around the Earth in about 3 weeks and attained global coverage by about 1 year after the eruption. Peak local midvisible optical depths of up to 0.4 were measured in late 1992, and globally averaged values were about 0.1 to 0.15 for 2 years. The large aerosol cloud caused dramatic decreases in the amount of net radiation reaching the Earth's surface, producing a climate forcing that was two times stronger than the aerosols of El Chichón. Effects on climate were an observed surface cooling in the Northern Hemisphere of up to 0.5 to 0.6°C, equivalent to a hemispheric-wide reduction in net radiation of 4 watts per square meter and a cooling of perhaps as large as -0.4°C over large parts of the Earth in 1992-93. Climate models appear to have predicted the cooling with a reasonable degree of accuracy. The Pinatubo climate forcing was stronger than the opposite, warming effects of either the El Niño event or anthropogenic greenhouse gases in the period 1991-93. As a result of the presence of the aerosol particles, midlatitude ozone concentrations reached their lowest levels on record during 1992-93, the Southern Hemisphere "ozone hole" increased in 1992 to an unprecedented size, and ozone depletion rates were observed to be faster than ever before recorded. The atmospheric impact of the Pinatubo eruption has been profound, and it has sparked a lively interest in the role that volcanic aerosols play in climate change. This event has shown that a powerful eruption providing a 15 to 20 megaton release of SO2 into the stratosphere can produce sufficient aerosols to offset the present global warming trends and severely impact the ozone budget.

If we could (somehow) pump sulphur dioxide into the stratosphere every year, mimicking a volcanic eruption, we would be able to reduce global temperatures by 0.5 degrees--at the cost of expanding the hole in the ozone layer (not good).  Who would pay for this?  The same people who now reject the switch to renewables "because it's too costly"?  And the solution is temporary: within a couple of years the SO2 aerosols will have fallen to earth as acid rain (also not good). 

Another kind of geo-engineering (though it's not often thought of that way) is to turn carbon dioxide to rock.  This is a permanent solution but will take massive effort and plenty of cash to make it happen.  The pilot plant in Iceland turned 220 tonnes of CO2 into rock.  But this equals the annual emissions of just 12 people in the US or Australia.  We would need 27 million similarly sized plants to turn the emissions of the USA to rock.

The best preventive to runaway global warming remains to replace fossil fuels in power generation and transport, to find different ways of making cement and steel, and to stop clearing and burning forests.  As fast as possible.

Volcanic vs human CO2 emissions

From Bradley Pitcher, vulcanologist.

November 3rd hottest on record despite La Niña

Source: RobertScribbler

The chart doesn't show the absolute temperature, it shows the anomaly.  Temperature anomalies are calculated by taking the temperatures for a place for each month  and then subtracting the average temperature for each month.  The base period for which the average is calculated differs for each authority, but the shape of the resulting charts is pretty similar.   V shows a significant volcanic eruption, m shows the sunspot minima and M the sunspot maxima.  There is some evidence that eruptions reduce temperatures (1911, 1982) but very little evidence a priori that the solar cycle has any impact.  One would expect sunspot minima to correspond to lower anomalies and vice versa with maxima, and there seems to be no relationship.

The lowest anomalies (the coolest periods) are at the beginning of the chart, the highest at the end, a clear sign of the rising temperature trend.  Because of random fluctuations, it's not a smooth transition from dark blue through yellow to pink.  March 1900, for example, was relatively warmer than the other months in 1900.  That doesn't mean it was warm, just that it was warmer than March is on average.

With data available for January through November this year it seems 98% likely that 2017 will edge out 2015 to be the second hottest year since the 1880s, despite a La Niña, which should cool the global atmosphere.  After the previous strong El Niño in 1998, global temepartures dropped significantly.  See how the long sequence of red squares in 1998 didn't happen again until 2005.  This time, despite a La Niña, temperatures have dropped only a little.  This is not good.

Big declines in CO2 emissions won't start for another decade, which means that global temperatures will keep on rising for at least that long.  The trend increase has been 0.2 degrees C per decade--they'll need one more colour on this chart.  The eruption of Mt Agung in Indonesia may lower temperatures for a while, as has happened with previous volcanic eruptions, but it won't last.  Look for lots more pink and black on this chart as it is updated over the next 10 years.  And keep the pressure up on your elected representatives.  If we had started reducing emissions 2 decades earlier we wouldn't be in the fix we are now.  We don't want another 2 decades of delay and denial.