Showing posts with label science. Show all posts
Showing posts with label science. Show all posts

Friday, 31 August 2018

A reminder that the world has known about the negative effects on the atmosphere of burning coal for over 100 years


Live Science, 14 August 2018:

A newspaper clip published Aug. 14, 1912, predicts that coal consumption would produce enough carbon dioxide to warm the climate.


Credit: Fairfax Media/CC BY-NC-SA 3.0 NZ

A note published in a New Zealand paper 106 years ago today (Aug. 14) predicted the Earth's temperature would rise because of 7 billion tons of carbon dioxide produced by coal consumption.

"The effect may be considerable in a few centuries," the article stated.
The clip was one of several one-paragraph stories in the "Science Notes and News" section of The Rodney and Otamatea Times, published Wednesday, Aug. 14, 1912.

The paragraph seems to have been originally printed in the March 1912 issue of Popular Mechanics as the caption for an image of a large coal factory. The image goes with a story titled "Remarkable Weather of 1911: The Effect of the Combustion of Coal on the Climate — What Scientists Predict for the Future," by Francis Molena. [Photographic Proof of Climate Change: Time-Lapse Images of Retreating Glaciers]

Wednesday, 6 June 2018

Australian climate change denying journalists are at it again


This was @SkyNewsAust, tweeting on 3 June 2018:

.@chriskkenny: Australia’s total carbon emissions is around 550 million tonnes. That is lower than the annual emissions from volcanoes. If our emissions go up or down, it will make precisely no difference to the planet. #kennyonsunday

News Corp journalist, author, former Liberal Party political adviser and Sky News host of "Kenny on Sunday", Chris Kenny is toying with comparisons in an attempt to downplay climate change facts and figures.

According to the Dept. of Environment and Energy Quarterly Update of Australia’s National Greenhouse Gas Inventory annual greenhouse gas emissions for 2017 stood at 531.9 million tonnes carbon dioxide equivalent (Mt CO2-e) by September that year.

That represents a 1.1 per cent increase in Australia’s annual emissions.

While according to U.S. National Oceanic and Atmospheric Administration; Since the start of the Industrial Revolution, human emissions of carbon dioxide from fossil fuels and cement production (green line) have risen to more than 35 billion metric tons per year, while volcanoes (purple line) produce less than 1 billion metric tons annually. NOAA Climate.gov graph, based on data from the Carbon Dioxide Information Analysis Center (CDIAC) at the DOE's Oak Ridge National Laboratory and Burton et al., 2013. [my highlighting and emphasis]

Leaving aside the fact that Australia has no active volcanoes so no direct comparison can be made between domestic man-made greenhouse gas emissions and domestic natural volcanic emissions, it is clear that the level of human emissions far exceed volcanic emissions at global levels.

It is also clear that a rise in Australia’s annual greenhouse gas emissions will have an impact, because carbon emissions are still rising globally and this country's annual increase is factored into that total global increase.

It is precisely that total global greenhouse emission figure which is definitely making a difference to the planet and, according to established climate science, that difference is already causing global warming induced problems world-wide.

No amount of sophistry will change that fact.

This was also  @SkyNewsAust tweeting on 3 June 2018:

.@rowandean: On the first day of the calendar winter we've also had a record breaking cold start to the season despite, only a day earlier, the climate change-loving Bureau reassuring us all how warm it would be.

News Corp journalist, magazine editor, author and Sky News commentator, Rowan Dean, is confused about what the term "record breaking" actually means.

On 1 June - the exact date of the start of calendar winter - in Sydney the lowest temperature was 13°C. The lowest recorded temperature for 1 June was 2.1°C in 1932 and the average minimum for June is 18.6°C. 

In Melbourne on the same day the lowest temperature was 3°C. The lowest June record for Melbourne was previously set at 3.3°C in 1937 and the average minimum for June is 6.9°C. 

Brisbane's lowest temperature on 1 June was 8°C. The lowest recorded June temperature for Brisbane was 5°C in 2001 and the average minimum for June is 10.9°C. 

So yes, it was a cold start to winter. However the cold was no across the board record breaker.

When it comes to what the Bureau of Meteorology (BOM) stated about Winter 2018 - it didn't state every single day would definitely be warm or warmer.

What it did state on 31 May 2018 was that:






 NOTES
*timeanddate.com at https://www.timeanddate.com/weather/australia for Sydney, Melbourne and Brisbane temperatures on 1 June 2018
*BOM at http://www.meteorology.com.au/local-climate-history for climate histories of Sydney, Melbourne and Brisbane
* http://www.eldersweather.com.au/climate.jsp

It doesn't take a genius to see that Sky News Australia (founded by Rupert Murdoch in 1989) appears to be running an anti-science agenda.

Wednesday, 11 April 2018

It seems climate change deniers may be looking to that far-right lobby group the Insitute of Public Affairs (IPA) to organise defence fund appeals in the future




For more than a decade, Ridd [Peter Vincent Ridd] has been happily criticising the science linking dangerous climate change to greenhouse gas emissions and the science showing the impacts of humans on corals.

Ridd has also repeatedly, over many years, said that the impact of agricultural runoff and water quality on the health and growth rate of corals is overstated.

But his employer, James Cook University, initiated its own action against Ridd after he had criticised specific organisations at his own university in media interviews, saying they could not be trusted. This, the university alleged, went against the university’s code of conduct.

So this is not about Ridd’s “freedom” to say what he wants but is about an alleged breach of the university’s code of conduct — whether you agree with that code or not.

When the university censured Ridd in 2016, he ignored them. He gave an interview in August 2017 to another climate science denier, Alan Jones, on Sky News. Ridd was there to talk about his chapter in a climate science denial book produced by the Institute of Public Affairs (IPA).

Ridd said 'we can no longer trust' the Government-backed Australian Institute of Marine Scienceand the Center of Excellence for Coral Reef Studies, based at James Cook University…..

The university alleged this constituted further “serious misconduct”, so Ridd took the issue to his lawyers and a case is proceeding.

To help fund his legal bills, Ridd got some help from the IPA (a key organisation pushing climate science denial in Australia for two decades) to set up a crowdfunding campaign that raised the necessary $95,000 in just 49 hours.

The IPA’s executive director John Roskam was the first donor with $500. Other notable givers included climate science denier and blogger Anthony WattsU.S. Interior Department employee and climate science denier Indur Goklany, Perth philanthropist and IPA funder Bryant Macfie and author and political scientist Don AitkenThe Washington Post and others have also reported how Goklany has had a key role in re-writing Department of Interior climate documents.

Many of Ridd’s cheerleaders have taken his scientific claims without scepticism and have not entertained the idea that he might be wrong.

Ridd’s marine pollution?

But Ridd repeated in detail several of his criticisms in a November 2017 "viewpoint" article in the journal Marine Pollution Bulletin — opening up his arguments for scrutiny.

Now, as reported in The Guardian Australia, a team of nine scientists, many based at the Australian Institute of Marine Science and the James Cook University centre Ridd has attacked, have issued a response through the same journal. Their assessment of Ridd’s claims is sharp.

They say Ridd’s criticisms are based on 'misinterpretation, selective use of data and over-simplification' and that they ignore 'formal responses to previously published critiques'.

Wednesday, 14 February 2018

Climate change sceptics started the ball rolling again in 2018


It would appear that climate change denial remains alive and well, but with the same hearing and comprehension problems it acquired at birth.........

The Daily Examiner and Townsville Bulletin, 10 January 2018:

In today’s crazy world, western politicians are wasting billions of taxpayer dollars force-feeding costly unreliable green energy in the bizarre belief this will somehow change Earth’s climate.

Even more incredible, they fear global warmth and seem hellbent on creating global cooling. They should study climate history. It is snow and ice, cold dry air and carbon dioxide starvation we need to fear, not a warm, moist, fertile, bountiful atmosphere.
Climate change is natural and unstoppable. Just 20,000 years ago, Earth was in one of its recurring glacial phases.

A thick massive ice sheet smothered Canada, Alaska, Iceland, Greenland, North Asia and Europe as far south as present-day London.

Much of the animal and plant life of the previous warm era was extinguished. Even in warmer lands not covered by the ice sheet, plants suffered as the cold oceans removed moisture and carbon dioxide plant food from the atmosphere.

Then, because of changing cycles in Earth’s orbit and tilt, reinforced by changing solar cycles, the sun warmed the frozen lands.

The great ice sheets melted, sea levels rose and the warming oceans expelled moisture and CO2 plant food into the atmosphere. Plant life recovered.

Tundra, forests, grasslands and herbivores advanced towards the pole and fish became abundant in the shallow seas that flooded coastal plains. Hunters, herders, farmers and fishermen followed the food.

Human population increased greatly. They gave thanks for the warmth, and worshipped the sun. But the peak of the modern warm era is past, and the natural cycles controlling global temperatures are pointing downwards.

Only an idiot with a death wish for life on Earth would attempt to accelerate our inevitable descent into the next ice age.

Luckily, their costly war on warmth is totally futile, but their war on carbon energy will prove tragically misguided in the cold times ahead.

VIV FORBES, Washpool, Qld

NOTE: According to DeSmog, “Viv Forbes is the Chairman of the Carbon Sense Coalition, which was created to “defend the role of carbon on earth and in the atmosphere,” and which describes Forbes as a “pasture manager, soil scientist and geologist from Rosevale in Queensland.” [2]
Forbes has also had a long association with the coal industry. According to his biography at Stanmore Coal where he acts as director, Forbes has over 40 years of coal industry experience and has worked with Burton Coal, Dalrymple Bay Coal Terminal, South Blackwater Coal Mine, Tahmoor Coal Mine, Newlands/Collinsville Coal Mines, MIM, Utah Goonyella/Saraji and Gold Fields.
He is also associated with other skeptical organizations including the International Climate Science Coalition (ICSC) and the Australian Climate Science Coalition (ACSC)
According to Forbes, the “Green Elite” has a “long-term agenda … to destroy human industry and reduce human population. Thus they are opposed to farming, mining, fishing, forestry, exploration and cheap power.” [3]

The Daily Examiner, 17 January 2018, p10:

Sceptic miscue

Savvy DEX readers certainly realise that sceptic science/climate denial mumbo jumbo has its origins in the ultra conservative religious right of the US political landscape.
Coincidentally but sadly for the rest of the world, many in the Trump administration are of this ilk.

Dedicated sceptic and Rosevale, Qld resident Viv Forbes has once again (DEX Jan 10) produced a pitch- perfect melody from the sceptic songbook.

As Viv points out, naturally occurring climate change takes place over thousands of years.

On the other hand, global warming is measurable over decades, is a direct result of human activity over the last century in particular and so is everything but natural.
Moreover, Viv is warning us of an impending frozen armageddan (in sceptic speak that should read OhMyGodden!)

I hope Viv appreciates that in the very same week as he made this dire forecast, the BOM has confirmed that 2017 was the warmest year on record for NSW and SE Queensland – timing is everything Viv.

The world may well cool in 25000 years or so, but world leaders rightly are more concerned with the immediate effects of global warming over the next few decades.
Nevertheless, we should probably remain grateful that Viv actually gets his name correct because everything else in his letter is nothing more than irrelevant nonsense.

Ted Strong, Seelands

The Daily Examiner, 27 January 2018, p15:

Tampered temperatures

TED Strong (17/1) commented: “As Viv Forbes points out, naturally occurring climate change takes place over thousands of years. On the other hand, global warming is measurable over decades, is a direct result of human activity over the last century in particular and so is everything but natural.”

Actually Viv said: “Climate change is natural and unstoppable.” He did not mention time, although the changes often occur rapidly.

During the Pleistocene Epoch, there have been many ice ages. The latest, which covered large portions of the northern hemisphere with mile-high ice, peaked 21,000 years ago and was gone by 11,700 years ago.

Since then there was the little Ice Age between 1400AD and 1850AD and a number of warm periods, which included two Holocene Optimums, the Roman Optimum from 250BC to 400AD, and the Medieval Warm Period from 800 to 1400. These four were as warm as, or warmer than, the Modern Warm Period, commencing around 1850.
So Ted could you explain what caused the previous warming periods, because they definitely weren’t “unnatural”?

But we keep being told that our current temperatures are the “hottest ever recorded”. So how do NOAA, NASA and the BOMs define “ever recorded”?

Our BOM stated: “…2017 was the third-warmest year on record, at 0.95 degrees above the 1961 to 1990 average” and that “Seven of the 10 hottest years, have occurred after 2005”.

Years ago the BOM decided temperatures taken before 1911 were “incorrect” and would no longer be taken into account. Obviously the 1890s temperatures were too high to explain.

But that left the 1939 era, which is still regarded as being the hottest since 1900. To overcome that pesky problem they established a baseline temperature using a 30-year average between 1961 and 1990.

This was a great choice because it included the chilly 1970s, when the world panicked that an ice-age was coming.

So our BOM, with a straight face, tells us that the “warmest on record” years have actually been selected from the last 28 years, and the 0.95 degree increase is based on the chilly 1961-1990 average.

So although the BOM openly says what period its figures are based on, it knows that the gullibles, and (unfortunately) the media, will submissively accept their fallacious statements as being from time immemorial.

JOHN IBBOTSON, Gulmarrad

The Daily Examiner, 31 January 2018, p11:

Climate warriors rattle cages

The war of words between the two climate change adversaries, one upriver and his opponent from down river, has reached a point where one party has delved into his “unseemly” bag to crudely criticise and try to belittle his opponent.

John Ibbotson can make his case with facts and figures garnered from research by Scientists that are not locked into the one eyed ideology that has evolved from the suspect science of climate change computer modelling.

Of course the Bureau of Meteorology can make mistakes, and has freely admitted to errors in the past, while Tim Flannery is an example of just how far off the planet these fear mongering so called gurus can get.

The scandal involving climate change scientists in the British Met in East Anglia will not go away nor will the fact that in the early 1990s temperature readings used to falsify average ground temperature data came from thousands of sites situated close by or near to, major heat sources such as American airports and bustling highways.
John Ibbotson makes his case in a calm and methodical way, Ted Strong just doesn’t like his precious cage being rattled.

FRED PERRING, Halfway Creek.

The Daily Examiner, 3 February 2018, p13:

Climate desperation

Blimey, things must be getting desperate in the John Ibbotson climate sceptic camp. He now has to rely on Fred Perring (DEX 31/1) for his great science knowledge.

PAUL STEPHEN, Yamba

The Daily Examiner, 7 February 2018, p11:

Wrong horse, wrong track

When compulsive scribe Fred Perring submits his favourites – ie maligning left-wing pollies or bashing the ABC – he does OK because the only requirements are bias, bluster and righteous indignation which Fred does in spades, while fact and logic seem to be of little consequence.

But when Fred comes out swinging, (DEX 31/1) in support of downriver sceptic, John Ibbotson, fact and logic become vital and so Fred flounders. Not only is he backing the wrong horse he is not even at, or on the right track.

The tiresome “facts” he trots out are Fred repeats, straight from the sceptic science hymn book and still unsupportable.

Even Fred’s well-known visually impaired namesake would by now have recognised that, particularly in the past decade, global warming is no less than the bleeding obvious.

Advice for Fred is the same as for John – stay away from sceptic websites and stick to the things you do best. Also thanks for the “heads-up” re my cage – I’ve checked it out and it appears quite solid if not completely foolproof.

TED STRONG, Seelands.

Friday, 5 January 2018

Climate denialists discuss suing a company for NOT increasing pollution


There are times when one wonders just how crazy the people associated with The Heartland Institute can get – then this sentence pops up a 6-page email from the Institute’s CEO Jim Bast to its Director of Communications Jim Lakely:

sue a company for not increasing CO2 emissions, force a court to consider the evidence on CO2 benefits.

The October 2017 email exchange can be read at https://www.documentcloud.org/documents/4112082-Joe-Bast-Email.html

A list of people on The Heartland Institute’s mailing list who would be receiving such suggestions, courtesy of DeSmog Blog:

Heartland Institute's Climate Scientists Mailing List
Heartland Institute's Climate Economists Mailing List 

As far-right global warming denialists in the Turnbull Government tend to mimic US moves against science-based policy, I suspect that this pared-down version of the latest Heartland playlist will be used in Australia in 2018 whenever they plan strategy or are quoted in the media on the subject of climate change:

* be briefing news reporters and news readers
* simplify the issue by focusing on one or only a few arguments and images
* identify a few good spokespersons and focus on promoting them
* stop chasing the other side’s latest argument and focus instead on the benefits of CO2
* focus on the “tuning scandal” that discredits the models
* turn debate from referring to median temperatures to high temperatures, which show no trend
* find independent funding for [insert climate change denier of choice]
* respond to [insert climate report of choice]
* get good people onto EPA advisory boards
* we need to be able to say “EPA is reconsidering whether CO2 is a pollutant”
* document instances where EPA etc. fail to cite research findings that contradict their agenda
* conduct a new survey of scientists to refute the 97% consensus claims
* sue a company for not increasing CO2 emissions, force a court to consider the evidence on CO2 benefits
* read The Business of America is Lobbying to understand the tactics of those we are really up against
* never use the phrases “windmill farms,” “all of the above,” “carbon pollution,” “social cost of carbon,” or “air pollution”
* use “industrial windmills,” “reliable and affordable,” “carbon dioxide emissions,” “benefits and costs of fossil fuels,” and “air quality”
* emphasize that we are pro-science and pro-environment… and the other side is not
* always think about what is most important to your audience
* when being interviewed, deliver your headlines first, don’t let the reporter lead you astray or cut you off
* prepare to answer the “what if you are wrong?” question with “what if you are wrong? How much damage will you have caused by costing the average household $4,000 a year for nothing?”
* fundamentally challenge, reform, or replace the [insert government agency of choice], the source of much pseudoscience
* stop funding “more research”
* clearly distinguish “safe” – a policy concept – from “risk” – a scientific concept, and keep scientists from pontificating on the former and advocates from misrepresenting the latter
* doubling the concentration of CO2 in the atmosphere would increase plant productivity by 35%.
* any SCC calculation that doesn’t include the benefits of CO2 should be rejected out of hand

Monday, 25 September 2017

World's most successful environmental agreement has been in place for thirty years this month


CSIROscope, 15 September 2017:  

This weekend marks the 30th birthday of the Montreal Protocol, often dubbed the world’s most successful environmental agreement. The treaty, signed on September 16, 1987, is slowly but surely reversing the damage caused to the ozone layer by industrial gases such as chlorofluorocarbons (CFCs).

Each year, during the southern spring, a hole appears in the ozone layer above Antarctica. This is due to the extremely cold temperatures in the winter stratosphere (above 10km altitude) that allow byproducts of CFCs and related gases to be converted into forms that destroy ozone when the sunlight returns in spring.

As ozone-destroying gases are phased out, the annual ozone hole is generally getting smaller – a rare success story for international environmentalism.

Back in 2012, our Saving the Ozone series marked the Montreal Protocol’s silver jubilee and reflected on its success. But how has the ozone hole fared in the five years since?

The Antarctic ozone hole has continued to appear each spring, as it has since the late 1970s. This is expected, as levels of the ozone-destroying halocarbon gases controlled by the Montreal Protocol are still relatively high. The figure below shows that concentrations of these human-made substances over Antarctica have fallen by 14% since their peak in about 2000.

Past and predicted levels of controlled gases in the Antarctic atmosphere, quoted as equivalent effective stratospheric chlorine (EESC) levels, a measure of their contribution to stratospheric ozone depletion. Paul Krummel/CSIRO, Author provided

Read the full article here.

Tuesday, 5 September 2017

NSW Berejiklian Government needs to face water sustainability issues on the Liverpool Plains


Santos Ltd plans to drill up to 850 coal seam gas production wells on 425 well pads in its Narrabri Gas Project located on approx. 95,000 hectares in the Pilliga State Forest and on private agricultural land south-west of Narrabri, NSW.

Project infrastructure will include a central gas processing facility for the compression, dehydration and treatment of the gas to commercial quality, along with infrastructure supporting treatment, beneficial reuse, power generation, water and gas distribution and operational management facilities.

Upon request the Independent Scientific Committee on Coal Seam Gas and Large Coal Mining Development has given advice to the Australian Government Department of the Environment and Energy and New South Wales Department of Planning and Environment concerning this project.

Here are some of the issues it raises in its 8 August 2017 advice:

Key potential impacts
The key potential impacts of the project include:
* long-term release of salt to the environment and the ongoing management of brine and salt waste. There is uncertainty in the quantities of salt that will be produced. There is also limited information in relation to the location and process for storage, and the containment and monitoring measures at the point of disposal.
* declines in groundwater level in landholder bores as a result of depressurisation and drawdown in the medium- to long-term (greater than 10 years).
* reductions in water availability to springs and other GDEs as a result of groundwater depressurisation and drawdown. These reductions may also impact surface water and groundwater connectivity, particularly along Bohena Creek.
* changes in surface water flow as a result of proposed discharges into Bohena Creek and uncertainties in the management of water during project operations in the short term (less than 10 years).
* changes to surface water and groundwater quality as a result of inappropriately stored or unintentional release of chemicals or untreated co-produced water.
The NSW Berejiklian Coalition Government needs to face the issues squarely, instead of pretending there is little to no risk to springs, aquifers and other ground and surface water under this mining application.

Saturday, 12 August 2017

Just because it is beautiful........(31)



The International Space Station moves across the face of the Earth's natural satellite, the Moon, photographed in broad daylight by Dani Caxete, BBC News, 2 August 2017

Tweet of the Week



Climate change denialist, anti-science and all round conspiracy theorist, discredited One Nation Senator Malcolm Ieuan Roberts gets disinvited.

Sunday, 16 July 2017

Chris Kenny and Andrew Bolt "wilfully misrepresent" according to Crikey and the scientific community


Crikey must have taken some pleasure in publishing this story on 11 July 2017:


…..But Kenny knew better, cleverly revealing the real story: “a global warming pause”.

Wrong. There is no global warming pause, as has been widely and repeatedly made clear, for example, herehere and here. Even worse, the paper he referred to said nothing of the sort.

About five seconds into Kenny’s TV, ahem, “report”, he decided to stop being even slightly accurate. “What they’re saying here is that the warming they have on their graphs, on their modelling, is much higher than the warming that has actually occurred.”  

The paper didn’t say this either.

Kenny then went on to quote repeatedly and triumphantly from the paper’s abstract, not the paper itself. Which is a bit weird. It’s like quoting from the back cover of a book, not the book itself. (The abstract of academic papers is typically publicly available, whereas the papers themselves are usually restricted to researchers or universities.) For such a huge, serious science story, wouldn’t you cite the actual paper? Unless, of course, you don’t have access to the paper. And if you don’t have access, have you actually read the thing?

Kenny quoted the last line of the paper’s abstract:

“We conclude that model overestimation of tropospheric warming in the early twenty-first century is partly due to systematic deficiencies in some of the post-2000 external forcings used in the model simulations.”

This, he said, meant that scientists were overstating temperatures. Hence the momentousness of his”story”. Problem is, the paper didn’t say this at all.

If he’d read the last line of the paper itself — and it’s questionable as to whether he read the paper at all — he would have read this:  

“Although scientific discussion about the causes of short-term differences between modelled and observed warming rates is likely to continue, this discussion does not cast doubt on the reality of long-term anthropogenic warming.”

Kenny didn’t report this, though. If he had, he wouldn’t have much of a story. However, he did claim that the paper showed that climate scientists’ models were wrong, that temperatures were overstated and therefore climate change wasn’t such a problem.

Kenny is the earthly representative of his spiritual mentor, Andrew Bolt, who misreported the same story, but went one further, saying that the paper’s lead author, “leading alarmist Ben Santer, now admits the world isn’t warming as predicted by global warming models”.

Not only is Bolt’s report as untrue as Kenny’s — if not more so — but Santer has been at pains to make clear the opposite is the case. For example, he published a fact sheet to accompany the paper Kenny and Bolt reported on. Wait a moment, I here you say, there was a fact sheet

Indeed. As Santer explained to me:

“The aim of the fact sheet was to reduce the likelihood of misinterpretation of key findings of our paper. But no matter how carefully or cautiously a paper is written, it is impossible to guard against wilful misrepresentation of results. Sadly, such wilful misrepresentation is now an expected outcome after each paper I publish.”…..

Apart from getting the names of two of the researchers right, little else Kenny said was.

As is evidenced by Kenny’s Heads Up segment posted on YouTube:


Here is that fact sheet both Kenny and Bolt appeared to ignore:

Benjamin D. Santer, John C. Fyfe, Giuliana Pallotta, Gregory M. Flato, Gerald A. Meehl, Matthew H. England, Ed Hawkins, Michael E. Mann, Jeffrey F. Painter, Céline Bonfils, Ivana Cvijanovic, Carl Mears, Frank J. Wentz, Stephen Po-Chedley, Qiang Fu, and Cheng-Zhi Zou
Published online in Nature Geoscience. DOI:10.1038/NGEO2973.
Question 1: What is the main issue that you look at in your paper?
Answer: Our paper looks at satellite and climate model estimates of global-mean changes in the temperature of the lowest layer of Earth’s atmosphere – the troposphere. It tries to understand why there are differences between modeled and observed tropospheric warming rates over the period of satellite atmospheric temperature measurements (January 1979 to December 2016). These differences have an interesting time signature. In the last two decades of the 20th century, differences between modeled and observed tropospheric warming were generally small. But during most of the early 21st century, the average warming in models was larger than in observations.
We asked whether such differences between modeled and observed warming rates could be explained by natural internal variability of the climate system. Natural internal variability arises from phenomena like El Niños, La Niñas, decadal oscillations in the Pacific,1 and the Atlantic Multidecadal Oscillation (AMO).
We found that natural internal variability can explain most of the relatively small differences between modeled and observed tropospheric warming in the last two decades of the 20th century, but can’t fully explain why model tropospheric warming is larger than in the satellite data during much of the early 21st century.
Question 2: What is your bottom-line finding?
Answer: The bottom line is that the differences between modeled and observed tropospheric warming contain useful diagnostic information. We use this information to test hypotheses about the causes of these warming rate differences. One hypothesis is that internal variability alone can explain why model tropospheric warming in the early 21st century is larger than in satellite data. Our findings suggest this hypothesis is very unlikely to be correct.
Based on our results, it is far more likely that the early 21st century differences between modeled and observed tropospheric warming rates are due to the combined effects of two factors: 1) Random differences2 1 Such as the closely-related Interdecadal Pacific Oscillation (IPO) and Pacific Decadal Oscillation (PDO). 2 We analyzed simulations performed with atmosphere-ocean models of the climate system, which produce their own random sequences of internal climate variability. In such models, there is no “synching up” (except by pure chance) between the random sequences of internal variability in the observations and in the model simulations. Different sequences of internal variability in “model world” and in the real world are not a scientific surprise – they are expected, and they can contribute to short-term differences between modeled and observed warming rates. 6/1/17 10:47 AM 2 in how modes of internal variability actually behaved in the real world and in the model simulations; and 2) The fact that some of the external cooling influences which affected “real world” temperature in the early 21st century were not accurately represented in the model simulations.
Question 3: What are the “external cooling influences” you are referring to in your paper?
Answer: Examples of such external cooling influences include a series of moderate volcanic eruptions, a long and unusually low minimum in the Sun’s energy output during the last solar cycle, and an uptick in particulate pollution from Chinese coal-fired power plants. The model simulations were performed before reliable, upto-date information became available about how these external cooling factors evolved in the early 21st century.3
Question 4: Do the problems in representing these external cooling influences point to systematic errors in how sensitive the models are to human-caused greenhouse gas (GHG) increases?
Answer: No, not at all. We are talking about known, well-studied problems with some of the external, climate-influencing “forcing factors” that were used in the model simulations. These problems have nothing to do with the issue of how sensitive models are to GHG increases.
Question 5: Haven’t some scientists claimed that the larger-than-observed model warming in the early 21st century is solely due to over-sensitive models?
Answer: Yes, such claims have been made and continue to be made. We tested the “over-sensitive models” claim in our paper, and found that it does not explain the actual differences between modeled and observed tropospheric warming behavior. Nor does a combination of “over-sensitive models” and natural internal variability plausibly explain the differences. None of our findings call into question the reality of long-term warming of Earth’s troposphere and surface, or cast doubt on prevailing estimates of the amount of warming we can expect from future increases in GHG concentrations.
Question 6: In a recent paper in Scientific Reports, you find that satellite measurements do not show any signs of “leveling off” of tropospheric warming over the past two decades. Aren’t those findings at odds with the findings of the Nature Geoscience paper?
Answer: No. The findings of the two papers are entirely consistent. The Scientific Reports paper compares the satellite tropospheric temperature trend over the past 20 years with many samples of 20-year trends obtained from model simulations of natural internal climate variability.4 Even though the most recent 20-year warming trend is smaller than in earlier parts of the satellite record,5 it is still significantly larger than the range of 20-year trends caused by internal climate variability alone. From our Scientific Reports study, there is no evidence that satellite data show “leveling off” of tropospheric warming in the last two decades.
The Nature Geoscience paper focuses on different model simulations. It looks at simulations of historical climate change, and asks whether differences between model-simulated and observed tropospheric warming 3 Consider a hypothetical climate model with perfect representation of all important physical processes in the real-world climate system. If such a model were used to simulate historical climate change, but the simulation left out important external cooling influences that affected the real world, the simulated historical warming would tend to be larger than observed. 4 Model estimates of natural internal variability were obtained from so-called “control runs”, with no year-to-year changes in GHGs, volcanic aerosols, the Sun’s energy output, or other external factors. 5 For reasons that are explained in the last paragraph of the answer to Question 2. 6/1/17 10:47 AM 3 could be due to different sequences of internal variability in the real world and in model world. It finds that internal variability alone cannot convincingly explain why models do a reasonable job capturing observed tropospheric temperature changes in the late 20th century, but not in the early 21st century. It also finds that “over-sensitive models” cannot explain the curious structure of model-versus-observed warming rate differences.
The key point here is that the two studies pose different scientific questions. The answers to these questions are complementary, not contradictory.
Question 7: What is the major remaining uncertainty in your study?
Answer: We think that the main uncertainty is in the model estimates of internal climate variability. We rely on these variability estimates to test the two hypotheses mentioned above – that differences between modeled and observed warming rates during much of the early 21st century could be due to: 1) internal variability alone; or 2) the combined effects of “over-sensitive models” and internal variability. If models systematically underestimated the size and the timescales of the major “real-world” internal variability modes, it would be less easy for us to rule out hypotheses 1 and 2.
The problem here is that satellite temperature records are relative short, and are a mixture of both internal variability and temperature responses to external factors (changes in GHGs, particulate pollution, the Sun, volcanic aerosols, etc.). Reliably teasing out the internal variability from such a short, mixed record is a tough job. To be clear: model control simulations6 can give us pure “unmixed” estimates of internal variability. Observations cannot, so there is some irreducible uncertainty in judging how well models capture key features of “real world” internal variability.
Previous work that we’ve done has not found a systematic low bias in model estimates of tropospheric temperature variability, but there is some evidence that current models might underestimate the timescale of the IPO. A lot more work needs to be done in comparing modeled and observed variability. We hope that our paper will provide impetus for such work.
Question 8: What are some of the major lessons you’ve learned?
Answer: One of the lessons learned is that “forcing matters”. Through the pioneering work of Susan Solomon and many others, we’ve learned a lot about the external influences that affected real-world temperature in the early 21st century. We now understand that if we systematically misrepresent these external influences in model simulations, we’ll see differences between modeled and observed warming rates. We need to do a better job understanding how these external influences actually changed in the real world, and we need to put our best estimates of these forcing factors into model simulations. This type of work is now happening.
Another valuable lesson learned is that “natural internal variability matters”, particularly when one is comparing modeled and observed temperature changes with different sequences of internal variability, and over short periods (1-2 decades). Many scientists (and many of the authors of the Nature Geoscience paper) have devoted years of their careers to the task of improving the understanding of internal variability.
These lessons will enable us to do two things. First, to more reliably separate internal variability and external influences in observed climate records. And second, to better quantify the relative contributions of internal variability and external influences to the differences between simulated and observed warming rates. The “lessons learned” will help us to better diagnose the causes of these differences.
FOOTNOTES
1 Such as the closely-related Interdecadal Pacific Oscillation (IPO) and Pacific Decadal Oscillation (PDO).
2 We analyzed simulations performed with atmosphere-ocean models of the climate system, which produce their own random sequences of internal climate variability. In such models, there is no “synching up” (except by pure chance) between the random sequences of internal variability in the observations and in the model simulations. Different sequences of internal variability in “model world” and in the real world are not a scientific surprise – they are expected, and they can contribute to short-term differences between modeled and observed warming rates.
3 Consider a hypothetical climate model with perfect representation of all important physical processes in the real-world climate system. If such a model were used to simulate historical climate change, but the simulation left out important external cooling influences that affected the real world, the simulated historical warming would tend to be larger than observed.
4 Model estimates of natural internal variability were obtained from so-called “control runs”, with no year-to-year changes in GHGs, volcanic aerosols, the Sun’s energy output, or other external factors.
5 For reasons that are explained in the last paragraph of the answer to Question 2.
6 See footnote 4.