Supercontinent Pangea was preceded by the formation of Gondwana, a “megacontinent”
about half the size of Pangea. There is much debate, however, over what role the assembly of the precursor megacontinent played in the Pangean supercontinent cycle. Here we dem- onstrate that the past three cycles of supercontinent amalgamation were each preceded by ∼200 m.y. by the assembly of a megacontinent akin to Gondwana, and that the building of a megacontinent is a geodynamically important precursor to supercontinent amalgamation. The recent assembly of Eurasia is considered as a fourth megacontinent associated with future supercontinent Amasia. We use constraints from seismology of the deep mantle for Eurasia and paleogeography for Gondwana to develop a geodynamic model for megacontinent assembly and subsequent supercontinent amalgamation. As a supercontinent breaks up, a megacontinent assembles along the subduction girdle that encircled it, at a specific location where the downwelling is most intense. The megacontinent then migrates along the girdle where it collides with other continents to form a supercontinent. The geometry of this model is consistent with the kinematic transitions from Rodinia to Gondwana to Pangea.
by Michigan Technological University, Jan 21, 2021 in ScienceDaily
NASA-funded research on the 11 largest freshwater lakes in the world coupled field and satellite observations to provide a new understanding of how large bodies of water fix carbon, as well as how a changing climate and lakes interact.
One of the most remarkable aspects of the results is just how fast changes in these freshwater lakes have occurred — a noticeable amount in fewer than 20 years. The research contributes to NASA’s Carbon Monitoring System’s goal of determining how much freshwater lakes contribute to the global carbon cycle.
“Three of the largest lakes in the world are showing major changes related to climate change, with a 20-25% change in overall biological productivity in just the past 16 years,” Fahnenstiel said.
More Than Algae
In the 16 years of data, Great Bear and Great Slave lakes in northern Canada saw the greatest increases in productivity, while Lake Tanganyika in southeastern Africa has seen decreases. The trends are linked to increases in water temperatures, as well as solar radiation and a reduction in wind speed.
Sayers said looking at productivity, algal abundance, water clarity, water temperature, solar radiation and wind speeds at freshwater lakes provides a richer picture of the overall ecosystem.
“Temperature and solar radiation are factors of climate change,” Sayers said. “Chlorophyll and water transparency changes are not necessarily caused by climate change, but could be caused by eutrophication or invasive species, like quagga mussels.”
by Rice University, Jan 21, 2021 in ScienceDaily
Crater study offers window on temperatures 3.5 billion years ago
Once upon a time, seasons in Gale Crater probably felt something like those in Iceland. But nobody was there to bundle up more than 3 billion years ago.
The ancient Martian crater is the focus of a study by Rice University scientists comparing data from the Curiosity rover to places on Earth where similar geologic formations have experienced weathering in different climates.
Iceland’s basaltic terrain and cool weather, with temperatures typically less than 38 degrees Fahrenheit, turned out to be the closest analog to ancient Mars. The study determined that temperature had the biggest impact on how rocks formed from sediment deposited by ancient Martian streams were weathered by climate.
The study by postdoctoral alumnus Michael Thorpe and Martian geologist Kirsten Siebach of Rice and geoscientist Joel Hurowitz of State University of New York at Stony Brook set out to answer questions about the forces that affected sands and mud in the ancient lakebed.
Data collected by Curiosity during its travels since landing on Mars in 2012 provide details about the chemical and physical states of mudstones formed in an ancient lake, but the chemistry does not directly reveal the climate conditions when the sediment eroded upstream. For that, the researchers had to look for similar rocks and soils on Earth to find a correlation between the planets.
by P. Homewood ,Jan 21, 2021 in NotaLotofPeopleKnowThat
If anybody tries to tell you that the computer models are accurately predicting global warming, show them this:
It comes from RSS, who monitor atmospheric temperatures via satellite observation. They are ardent warmists, and here us what they have to say:
by Cap Allon, Jan 20, 2021 in Electroverse
The start of 2021 in Antarctica has been an unusually chilly one. In fact, the first half of January has been the coldest since 1978, according to data compiled by @LpdlcRamirez and @peikko763 on Twitter.
As of Jan. 19, the month-to-date temperature anomaly across Antarctic is approx. -0.5C, making this the continents coldest first 3-or-so-weeks of Jan. since 1978 (solar minimum of cycle 20), according to research conducted by @peikko163 on Twitter, who also notes that the Southern Hemisphere as a whole is suffering anomalous January chills not seen since 2012.
But this chill of solar minimum isn’t just confined to the Southern Hemisphere either, the mercury ACROSS the planet is tumbling. In one month global temperatures dropped by a whopping 0.26C: from 0.53C above the 1981-2010 avg. in Nov. 2020 to just 0.27C above the avg. in Dec. 2020 (UAH). This drop was in spite of a warming Arctic–a region expected to “heat” during times of otherwise “global” cooling (more on that below).
The Sun appears to be sliding into its next Grand Solar Minimum cycle–a multidecadal spell of reduced solar output where the solar disc can be devoid of sunspots for months or even years at a time. The result on Earth’s climate will be one of violent swings between extremes due to a weakening of the jet streams: intense bursts of heat will linger in one area, while a teeth-chattering chill will dominate nearby, and then the regions will “switch” — it is this unpredictable chopping and changing that will hasten the failure of our modern food production systems: crops will fail, on a large scale, and famine could quickly ensue.
Overall, Earth’s temperature trends colder during a Grand Solar Minimum, as the Sun’s output sinks lower and lower (increased cloud nucleation being one likely forcing). However, not ALL regions experience the chill: as with the previous GSM (the Maunder Minimum 1645-1715), areas such as the Arctic, Alaska, and S. Greenland/N. Atlantic actually warmed while the rest of the planet cooled — NASA reveals the phenomenon in their Maunder Minimum temperature reconstruction map:
by P. Homewood, Jan 18, 3021 in NotaLotofPeopleknowThat
Many of you will be familiar with the work of Bob Tisdale over the years, concerning the mechanism of ENSO (ie El Ninos and La Ninas) and its effects on climate.
His seminal series of videos, recorded in 2012 is still on YouTube, and is still highly relevant.
Above is Part 1, which is worth sticking with all the way through, but otherwise the first 8 minutes is definitely worth a watch. Nothing has effectively changed since 2012, and Bob’s conclusions are still relevant and valid.
As well as explaining what exactly drives El Ninos and La Ninas, he makes some significant points:
Worldwide sea surface temperature trends since 1980 show no correlation with GHGs (see chart below)
Instead they exhibit a series of step changes up, which follow the major El Nino events of 1982/83, 1987/88 and 1997/98
Contrary to popular belief, global SSTs do not drop during La Nina episodes. This is because El Ninos transfer a vast amount of warm, subsurface water to the surface, where it remains during La Nina.
Some of this warm water in the East Pacific finds its way into the West Pacific and Indian Oceans. But through a process called teleconnection, SSTs is the Atlantic, where there is no direct connection, also rise and exhibit the same step changes.
Between major El Nino events, SSTs outside the East Pacific do not rise.
In the East Pacific, there has been no trend increase in SST at all since 1980.
by P. Homewood, Jan 17, 2021 in NotaLotofPeopleKnowThat
Using well documented data on the infra-red absorption spectra of atmospheric gases it is a straight-forward process to infer the overall atmospheric IR absorption and from that the effective global average temperature. The simplest of atmospheric models has been used: the atmosphere is considered to be a uniform thin absorbing layer of gas. The results demonstrate clearly that the warming effect of the atmosphere is almost entirely due to the spectral absorption characteristics of CO2 and H2O. They are both exceptionally strong absorbers of infra-red radiation. It is however this strength which determines the characteristics of the earth’s temperature, and in particular its stability.
70% of the energy radiated from the earth is removed by a mixture of 0.1% H2O and 200ppm of CO2. This alone is sufficient to raise global temperatures from the chilly 255K of the estimated zero atmosphere condition to 284.3K, less than 4deg below current average temperatures. An estimation of the current atmospheric mixture of gases is calculated to deliver a global mean temperature of 286.8K close to the best estimate of 288K for that temperature. Further increases in both H2O and CO2 have relatively small impacts on temperatures. This is due simply to the fact that at current concentrations the spectra of both H2O and CO2 have effectively extracted most of the energy at wavebands corresponding to their molecular absorption spectra. There is little further energy to be extracted by adding more H2O and CO2. This results in climate sensitivity values of less than 0.5degC, in comparison to the 1.5 to 5 degC range quoted by the IPCC.
CO2 levels of 3000ppm will only raise temperatures by a further 1.5K. These temperature increases are in fact well within natural variations seen in the past, including the medieval warm period and the little ice age of some 300 years ago.
The possibility of positive feedback from water vapour is discounted by the simple fact that the H2O spectrum is incapable of absorbing significant further amounts of radiated energy and the modest increase in temperature due to increasing CO2 levels is unable to deliver any significant increase in H2O concentration due to the specific relationship of H2O saturation vapour pressure and temperature. It would take an increase in temperature of 10degC to double the mean H2O atmospheric concentration, and that doubling would only result in a temperature increase of 2degC.
The impact of other known “greenhouse’ gases, CH4 and N2O are also calculated from known IR spectra data. Their absorption spectra are swamped by H2O and CO2. The combined warming caused by current atmospheric concentrations will elevate temperature by only 0.2K and increasing concentrations by a factor of 10 will only result in a further temperature increase of 0.5K.
The “greenhouse effect” is dominated by the absorption spectrum of H2O with a little help from CO2. At current concentrations of both gases it is inconceivable that further increases in concentrations will lead to any significant warming. Increasing CO2 concentration to 3000ppm and doubling the mean H2O level to 2% would result in a global temperature increase of 3.4K.
The full paper can be read here:
See this Addendum
by Nic Lewis, Jan 19, 2021 in ClilmateEtc.
- The pattern effect is the dependence of outgoing radiation to space on the spatial pattern of surface warming.
- A pattern effect, relative to that in equilibrium, can be caused both by evolution over time in the climate system’s response to forcing and by its internal variability.
- The paper fails to distinguish between a historical period pattern effect that is forced, which will unwind very slowly, and one that is caused by internal variability, which can quickly unwind, causing rapid warming.
- The forced pattern effect is very small in CAM5.3
- The pattern effect found in the paper is greatly affected by being estimated during the hiatus.
- The estimated post-hiatus unforced historical pattern effect is non-negligible in CAM5.3 when using the AMIP2 sea surface temperature dataset, as in the paper, but negligible when using the UK Met Office HadISST1 dataset.
- The historical pattern effect is not robust; it varies hugely between models and SST datasets.
- The paper’s claims about greater committed warming directly reflect its estimate of the size of the historical pattern effect.
A new paper “Greater committed warming after accounting for the pattern effect” led by Chen Zhou (Zhou et al.) has recently been published in Nature Climate Change. Here is the accompanying press release.
by RFI, Jan 12, 2021 in GWPF
A new report published in the US journal Science, led by the Chinese Academy of Sciences, suggests the world’s oceans are warming 40 percent faster than what a UN panel predicted five years ago. Although data collection is more accurate than in the past, some experts advise against jumping to hasty conclusions.
About 93 percent of excess heat trapped around the Earth by greenhouse gases that come from the burning of fossil fuels accumulates in the world’s oceans.
The UN Intergovernmental Panel on Climate Change (IPCC) says ocean warming has led to rising sea levels and contributes to increases in rainfall intensity, more violent storms and the destruction of coral reefs.
It is also a threat to biodiversity and one of the earth’s major food supplies.
“Ocean heating is a very important indicator of climate change, and we have robust evidence that it is warming more rapidly than we thought,” said co-author Zeke Hausfather, a graduate student in the Energy and Resources Group at the University of California, Berkeley.
Their report relied on four studies, published between 2014 and 2017 whose conclusions are based on measurements recorded by a fleet of some 4,000 floating robot monitors called Argo.
The robots drift throughout the world’s oceans, every few days diving to a depth of 2,000 meters and measuring the ocean’s temperature, pH, salinity and other information.
Argo “has provided consistent and widespread data on ocean heat content since the mid-2000s,” the report said.
The new analysis shows warming in the oceans is on pace with measurements of rising air temperature.
And if nothing is done to reduce greenhouse gases, “models predict that the temperature of the top 2,000 meters of the world’s oceans will rise 0.78 degrees Celsius by the end of the century,” it said.
Caution needed when interpreting results
David Whitehouse, the science editor for the Global Warming Policy Forum, based in the UK says we must very careful when drawing conclusions.
by P. Homewood, Jan 16, 2021 in NotaLotofPeopleKnowThat
Cancel all the claims by climate activists that global warming is decimating Antarctica. A peer-reviewed study recently published in one of the most prominent science journals destroys one of the most frequently asserted claims by climate activists – that climate change is warming Antarctica and melting the Antarctic ice sheet. The recent study confirms Antarctica has not warmed in the past 70 years and Antarctic ice cover is expanding rather than shrinking.
Writing in the journal Nature, scientists at Columbia University and the University of Victoria, British Columbia report, “The Antarctic continent has not warmed in the last seven decades, despite a monotonic increase in the atmospheric concentration of greenhouse gases.”
by Cap Allon, Jan 23, 2021 in Electroverse
Following the historic snowstorms of the past few weeks, Japan has been hit again: at least 13 people died and more than 250 were injured as record snowfall blanketed regions along the Sea of Japan coast, according to the latest report by the nation’s Disaster Management Agency.
Among those to have lost their lives were three people in Fukui Prefecture, and four in Niigata Prefecture, all reportedly while trying to remove the snow which topped a whopping 3.13 meters (10.3 feet) in some areas.
According to Japan’s Meteorological Agency (JMA), at least 10 monitoring stations along the Sea of Japan set new all-time 72-hour snowfall records late on Jan. 10, and many more busted all-time low temperature records, including in Furue, Kamigoori, and Kuzakai–with the latter logging a bone-chilling -24C (-11F).
by R. Pielke & J. Richtie, 2020 in EnergyRes&SocScience
Climate science research and assessments under the umbrella of the Intergovernmental Panel on Climate Change (IPCC) have misused scenarios for more than a decade. Symptoms of misuse have included the treatment of an unrealistic, extreme scenario as the world’s most likely future in the absence of climate policy and the illogical comparison of climate projections across inconsistent global development trajectories. Reasons why such misuse arose include (a) competing demands for scenarios from users in diverse academic disciplines that ultimately conflated exploratory and policy relevant pathways, (b) the evolving role of the IPCC – which extended its mandate in a way that creates an inter-relationship between literature assessment and literature coordination, (c) unforeseen consequences of employing a temporary approach to scenario development, (d) maintaining research practices that normalize careless use of scenarios, and (e) the inherent complexity and technicality of scenarios in model-based research and in support of policy. Consequently, much of the climate research community is presently off-track from scientific coherence and policy-relevance. Attempts to address scenario misuse within the community have thus far not worked. The result has been the widespread production of myopic or misleading perspectives on future climate change and climate policy. Until reform is implemented, we can expect the production of such perspectives to continue, threatening the overall credibility of the IPCC and associated climate research. However, because many aspects of climate change discourse are contingent on scenarios, there is considerable momentum that will make such a course correction difficult and contested – even as efforts to improve scenarios have informed research that will be included in the IPCC 6th Assessment.
by E. Worall, Jan 9, 2021 in WUWT
Apparently the Great Barrier Reef is so dead from climate change it needs teams of well funded scientists to run around planting coral. Except for the embarrassingly healthy bits Peter Ridd photographed, of course.
by E. Worall, Jan 7, 2021 in WUWT
According to Patric Seifert, a tropospheric researcher at the Leibniz Institute in Germany, a large scale temperature spike occurred just before the onset of the Little Ice Age. Seifert does not think global temperatures are about to crash, but he thinks conditions in Europe are similar enough to the 14th century that historical reconstructions of this medieval heatwave, the Dantean Anomaly, can help us understand what we will face as the world continues to warm.
Extreme 14th Century Droughts May Provide Insight Into Our Climate Change Crisis
9 JANUARY 2021
Scientists are studying a major, once-in-a-century drought from Medieval Europe to better understand how extreme weather events indicate rapid climate changes.
In the years leading up to the Little Ice Age, between 1302 and 1307, many regions on the European continent were facing exceptional heat and drought, according to historical records and data collected from tree rings and sediment cores.
These extreme natural events, while not driven by human emissions, hold similar characteristics to recent weather anomalies, and they could help us better predict the course of modern-day climate change.
“Even if it was a phase of cooling in the Middle Ages and we are now living in a phase of [hu]man-made warming, there could be parallels,” says Patric Seifert, a tropospheric researcher at the Leibniz Institute in Germany.
“The transitional period between two climate phases could be characterized by smaller temperature differences between the latitudes and cause longer-lasting large-scale weather patterns, which could explain an increase in extreme events.“
by P. Homewood, Jan 6, 2021 in NotaLotofPeopleKnowThat
The storm ‘Filomena’ leaves the lowest temperature ever recorded in the Iberian Peninsula: –34.1C
Temperatures in Spain this winter are reaching maximum levels. This week has been very cold, with frosts in much of Spain even in areas very close to the coast. The early morning of this Wednesday was marked by intense cold and snowfall. The thermometers show such low figures that the temperature at the Clot de la Llança (Alto Aneu) weather station stands out: – 34.1 degrees.
It is the lowest temperature in the Iberian Peninsula since there are records. Information provided by the Parc Natural de l’Alt Pirineu (managed by Meteo Pirineo and Meteo Valls d’Àneu). And it has also been confirmed by AEMET. This temperature, 34.1 degrees below zero, is a record since the last time something similar was recorded was on February 2, 1956 with -32.0ºC in Estany-Gento, in the province of Lleida,
See also here
by C. Rotter, Jan 7, 2021 in WUWT
Alps ice-free…6000 years ago, when CO2 was much lower than today’s levels.
Dr. Sebastian Lüning earlier today released his latest Klimaschau report, No. 6. In the first part he looks at glaciers in the Alps over the course of much the Holocene.
See the video
It turns out that Most of the Alps were ice-free 6000 years ago, glaciologists have discovered.
In his video, the German geologist presents a new paper authored by glaciologists Bohleber et al, 2020 of the Austrian Academy of Science. The Austrian-Swiss team discovered from ice cores that the 3500-meter high Weißseespitze summit was ice free 5900 years ago.
Much warmer in the early Holocene
Lüning next shows why the Alps were ice-free 6000 years ago by using a chart by Heiri et al 2015, which shows it was some 2°C warmer than today.
by Polar Bear Science, Jan 8, 2021 in WUWT
As well as summarizing sea ice changes, NOAA’s 2020 Arctic Report Card features two reports that document the biggest advantage of much less summer sea ice than there was before 2003: increased primary productivity. Being at the top of the Arctic food chain, polar bears have been beneficiaries of this phenomenon because the Arctic marine mammals they depend on for food – seals, walrus and bowhead whales – have been thriving despite less ice in summer.
In the sea ice chapter (Perovich et al. 2020), my favourite of all the figures published is the graph of September vs. March sea ice (above). As you can see, March ice extent has been virtually flat (no declining trend) since 2004. And as the graph below shows, September extent has been without a trend since 2007, as NSIDC ice expert Walt Meier demonstrated last year (see below): it doesn’t take much imagination to see that the value for 2020 from the graph above (the second-lowest after 2012) hasn’t changed the flat-trend line.
by Cap Allon, Jan 7, 2021 in Electroverse
The mercury in China’s capital Beijing plunged to -19.6C (-3.3F) on Thursday morning, January 7 as the powerful Arctic air mass currently gripping the majority of Asia intensified further.
The reading marked the capital’s coldest temperature since 1966 (solar minimum of cycle 19), in record-books dating back to 1912.
Furthermore, 10 out the 20 national-level meteorological stations in Beijing registered their lowest-ever early-January temperatures Thursday morning.
Blue alerts remain in effect across much of China as record low temperature and heavy snow are forecast to linger, at least until the weekend.
The intense cold wave began in mid-December, and is the result of Arctic air spilling down over the Asian continent (see low solar activity and meridional jet stream). Many all-time cold records have fallen across China of late…
by Dr J. Lehr & T. Ciccone, Jan 5, 2021 in ClimateChangeDispatch
The accuracy and integrity of weather and climate measurements have always been a concern. However, errors and omissions were not as consequential in the past as they are now.
A hundred or even fifty years ago, our major weather concerns were more limited to local weather. When we have a flight from NYC to LAX, we need to know more detailed and reliable weather information, like is it snowing in St. Louis where we have a layover?
Or the farmer in Nebraska who needs to see the spring wheat production forecast in Ukraine. He needs the best possible information to better estimate the number of acres of winter wheat he should plant for today’s global markets.
We especially need better and more reliable information to decide what actions we should consider preparing for climate changes.
While scientists, engineers, and software programmers know the importance and the need for this data accuracy, the general public is not aware of how challenging these tasks can be.
When looking at long term climate data, we may have to use multiple proxies (indirect measures that we hope vary directly with weather), which add an extra layer of complexities, costs, and sources of error.
One of the most commonly used proxies is the ancient temperature and CO2 levels from ice core samples. Also, for the last few hundred years, tree-ring data was a primary source of annual temperatures.
by F. Menton, Jan 5, 2021 in ClimateChangeDispatch
Some commenters yesterday noted that the climate establishment has not just completely ignored the threat to their orthodoxy posed by the Medieval Warm Period and other similarly-warm pre-human-emissions eras.
Initially, there was a recognition that this issue could be important, and there was definitely some attempt to deal with it.
However, over time, the accumulation of evidence, particularly as to the existence Medieval Warm Period as a global phenomenon, gradually became overwhelming.
So — in the face of evidence that, under the normal precepts of the scientific method, would be deemed to invalidate the hypothesis that only human CO2 emissions could be causing current warming — how can the orthodoxy be kept alive?
The answer, almost entirely, has been to resort to the hand-waving of “detection and attribution” studies, and hope nobody notices. And, to a remarkable extent, nobody notices.
Readers may be interested in a short history of this issue.
by P. Homewood, Jan 6, 2021 in NotaLotofPeopleKnowThat
When Donald Trump offered to buy Greenland from Denmark in 2019 it was dismissed as illegal and absurd. However, the president’s expression of interest was far from absurd, says Guillaume Pitron. Under its soil Greenland boasts one of the largest concentrations of the rare metals that the world will need to power electric cars, computers, mobile phones, robots, solar power plants, artificial intelligence and many high-tech “green” innovations that have not been dreamt up yet. If Trump were after those minerals, buying Greenland would have been a smart move.
The global production and sales of rare metals are dominated by China. It mines so much of them on home soil and controls so much of their extraction in Africa and elsewhere that it oversees up to 95 per cent of the global production of certain minerals. This puts Beijing in charge of “the oil of the 21st century”, writes Pitron, which is a problem for western nations because it means China can restrict supply and drive prices up or down at will, as Opec does with oil. We have “entrusted a precious monopoly of mineral sovereignty to potential rivals”, he notes.
Discarded devices waiting to have their precious metals extracted
CHARLY TRIBALLEAU/GETTY IMAGES
Rare earth minerals production is very energy intensive. Extracting a single kilogram of some requires mining as much as 1,200 tonnes of rock. “Clean energy is a dirty affair,” Pitron writes. He drives home his point by touring villages near polluted lakes in China that are known locally as “cancer villages”.
by B. Van Vliet-Lanoë, Jan 1, 2021 in ScienceClimatEnergie
Un hiver froid s’annonce : le premier d’une série qui devrait durer au moins jusqu’en 2053 (Youssef et al., 2009 ; Zharkova et al. 2015 ; Van Vliet, 2019), période où les médias nous assènent une disparition de la banquise estivale, des ours polaires et des phoques ! Ceci est favorisé par l’activité solaire réduite depuis et le minimum solaire actuel (Fig.1). Le cycle solaire suivant (n°25) devrait aussi être faible. Nous y sommes entrés sans un Minimum d’activité aussi profond que celui Dalton (1790-1830) qui a présidé à la « Bérézina ».
Fig. 1: Intensité des cycles solaires depuis 1975 et la prédiction du cycle 25 (calculés avec le nombre de taches solaires 2018 * ANRPFD ). B) évolution de l’extension en km2 des banquises arctique et antarctique depuis 1978 par rapport à la déviation standard 1981-2010 (NSDIC).
by C. Rotter, Jan 2, 2021 in WUWT
Many climate alarmist’s failed predictions were centered around 2020. This video examines just ten, and argues that they were produced not by science, but by ideology. This is proved by the fact that rather than suffering any consequences to their careers or public standing, fearmongering individuals and institutions enjoy continued and undeserved success. The analysis of the ten predictions was produced by Steve Milloy and can be read at his website:
- by Dr S. Lüning, Jan 3, 2020 in NoTricksZone
In his latest video the veteran geologist looks at wild fires worldwide and the CO2 they emit. He reports that both have been decreasing.
Citing the results of the European Copernicus satellite atmosphere monitoring service (CAMS), total wildfires globally have fallen steadily, along with their corresponding CO2 emissions: