Showing posts with label baseline. Show all posts
Showing posts with label baseline. Show all posts

Tuesday, February 20, 2018

IPCC seeks to downplay global warming

The graph below shows global warming for a 30-year period centered on January 2018, using NASA 2003 to January 2018 LOTI anomalies from 1951-1980, adjusted by 0.59°C to cater for the rise from preindustrial to 1951-1980, and with a polynomial trend added.

From: ECMWF Nino Plumes
Above graph shows that the 1.5°C guardrail, set at the Paris Agreement, was crossed in 2016 and that a 10°C (18°F) warming could eventuate within a decade or so.

The variations in above temperature data are strongly influenced by El Niño/La Niña. We currently are in a La Niña period, during which surface temperatures are suppressed, whereas surface temperatures in 2016 were much above the trendline, due to El Niño.

The ECMWF forecast from 1 February 2018 on the right indicates that we're heading for another El Niño, i.e. surface temperatures will be rising strongly over the coming months.

The IPCC seeks to downplay the amount of global warming that has already occurred and that looks set to eventuate over the next decade or so. A leaked draft of the IPCC 'Special Report on 1.5°C above pre-industrial' (First Order Draft of SR1.5 SPM) estimates that the global mean temperature reached approximately 1°C above pre-industrial levels around 2017/2018. The IPCC appears to have arrived at this estimate using an extrapolation or near term predictions of future warming so that the level of anthropogenic warming is reported for a 30 year period centered on today.

This 1°C IPCC estimate looks quite incredible when calculating the temperature rise using NASA's data for the two most recent years for which data are available (2016/2017), which shows a warming of 0.95°C when using a baseline of 1951-1980 and a warming of 1.23°C when using a baseline of 1890-1910.

Indeed, the temperature rise differs depending on which baseline is used, and when using preindustrial as a baseline, i.e. the baseline agreed to at the Paris Agreement, indications are that temperatures have already risen by more than 1.5°C, as also discussed in an earlier post.

Furthermore, when using a 30-year period centered on January 2018, the current temperature will have to be calculated over the past 15 years and estimated for the next 15 years, i.e. up to the year 2033.

To arrive at a 1°C rise for the 30-year period, the IPCC must somehow assume that temperatures will magically fall dramatically over the next 15 years, whereas indications are that temperatures will instead rise dramatically over the next decade or so.

The image on the right shows that 10°C (18°F) warming from preindustrial could eventuate within one decade when taking into full account the warming that could result from the elements depicted in the stacked bar. Each of these warming elements is discussed in more detail at the extinction page.

The image below shows the rise from 1750 to 2030, in surface temperatures (land+ocean), rather than in anomalies.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan.

Saturday, May 28, 2016

How Much Warming Have Humans Caused?

How much did temperatures rise since 1900?

Differences in baseline (reference period) can result in dramatic differences in temperature rise. The U.K. Met Office HadCRUT4 dataset typically presents temperature anomalies relative to a 1961-1990 baseline. NASA typically uses a 1951-1980 baseline, but the NASA website allows for different baselines to be selected. When selecting a 1961-1990 baseline, the temperature of the past period of six months was 1.05°C (1.89°F) higher than this baseline, as illustrated by the NASA map in the left panel of the image below. But when compared to 1890-1910, the temperature of the past period of six months was 1.48°C (or 2.664°F) higher, as illustrated by the NASA map in the right panel of the image below.

A polynomial trend can reduce variability such as caused by volcanoes and El Niño events. The graph below was created with the NASA L-OTI monthly mean global surface temperature anomaly, which has a 1951-1980 baseline, and then with 0.29°C added, which makes the anomaly 0°C in the year 1900 for the added polynomial trend.

This gives an idea of how much temperatures have risen since the year 1900, with a rise for both February and March 2016 showing up that was more than 1.5°C, as also illustrated by the image below. The trend further points at temperature anomalies that will be more than 1.5°C (from 1900) within a decade and more than 2°C soon thereafter.

Temperature Rise before 1900

To see by how much temperatures have risen compared to pre-industrial levels, we need to go back further than 1900. The graph below shows that carbon dioxide concentrations have gone up and down between levels of roughly 180 ppm and 280 ppm over the past 800,000 years. Recently, carbon dioxide levels reached a peak of well above 400 ppm (411 ppm peak hourly average on May 11, 2016).

The image below, from an earlier post, shows how in the past, over the past 420,000 years, temperatures have gone up and down within a window of approximately 10°C (18°F), in line with cycles in the Earth orbit (Milankovitch cycles). Levels of carbon dioxide and methane have gone up and down accordingly, with carbon dioxide moving between 180 ppm and 280 ppm and methane roughly between 300 ppb and 700 ppb.

Meanwhile, carbon dioxide concentrations have been as high as 411 ppm (as discussed further above), i.e. a 131 ppm rise on top of the historic maximum of 280 ppm. The rise in methane concentrations is even steeper, as discussed at the Methane page.

Has the rise in greenhouse gases due to emissions by humans set the scene for a temperature rise of some 10°C (18°F) above 1750 levels, and how rapidly could such a temperature rise eventuate? Could warming caused by humans result in a temperature rise of more than 10°C (18°F) within a decade?

In its First Assessment Report, the IPCC explains that temperatures have come down since the Holocene peak, i.e. the natural maximum of the most recent Milankovitch cycle (image right, top panel). As the bottom panel shows, temperatures have risen since the 1600s. There has been a rise from the year 1750 to the year 1900 and there has been a further rise from the year 1900 onward up to recent times (the dotted line indicates the temperature at the year 1900).

The graph on the right, created by Jos Hagelaars, shows that temperatures started rising some 20,000 years ago, reaching a peak some 7000 years ago (in the blue part of the graph). For more detail, also see the comic added at the end of this post.

The graph underneath, based on work by Marcott et al., focuses on this blue part of the graph, while using a 1961-1990 baseline. Temperatures reached a peak some 7000 years ago, and then came down to reach a low a few hundred years ago.

The peak and the bottom temperatures (highlighted in red on image on the right below) for that period suggest there was a fall of more than 0.7°C.

So, a few hundred years ago, temperatures were falling and they would have kept falling, in line with the Milankovitch cycles, had there been no warming caused by humans.

From that bottom point, temperatures first rose by about 0.4°C, overwhelming the downward trend that would otherwise have taken temperatures down further, and then there was an additional rise of at least 1.05°C, when using a baseline of 1961-1990, indicating that humans caused a total of at least 1.45°C warming.

Lewis & Maslin (2015) suggest that, because CO2 began to rise from a low point in 1610, that year could be taken as the start of the Anthropocene. The image on the right also shows that the year 1750 was a low point for CO2 levels and temperature, i.e. well below the baseline of 1961-1990.

The image below shows Northern Hemisphere temperature reconstructions by Moberg et al.

The image on the right is from The wider fluctuations back in time reflect volcanic activity and greater uncertainty, while a simple fit shows a temperature rise of 1.5°C in the past 250 years (1750-2000), of which about 0.9°C occurred in the past 50 years.

Humans have caused even more warming?

The situation looks to be even worse than what the above figures may suggest. Indeed, the bottom low point in the Marcott graph would have been even lower had there been no warming by humans.
The fact that humans did cause substantial warming between 1800 and 1900 is illustrated by the graph below, from a recent post by Michael Mann, who adds that some 0.3°C greenhouse warming had already taken place between the year 1800 and the year 1900.

Some 0.3C greenhouse warming had already taken place by 1900, and some 0.2C warming by 1870
Further studies suggest that humans also caused substantial warming well before 1800, as illustrated by the image on the right. While this study focuses on Europe, it does suggest a rise from 1600 to 1800.

Another example of warming caused by humans before 1800 is presented in research by Dull et al., which suggests that burning of Neotropical forests increased steadily in the Americas, peaking at a time when Europeans arrived in the late fifteenth century. By 1650, some 95% of the indigenous population had perished. Regrowth of forests led to carbon sequestration of some 2 to 5 Pg C, thereby contributing to a fall in atmospheric carbon dioxide recorded in Antarctic ice cores from about 1500 through 1750.

Since at least the fourth century A.D., coal has
been burned in China. W. F. Ruddiman further points in a 2007 paper at human emissions from burning biomass and irrigation, livestock and human waste, and the resulting climate system feedbacks. As illustrated by the image on the right, this had already caused substantial warming prior to the industrial revolution.

In conclusion, substantial warming took place before 1900, making that temperatures were higher than what they would have been had humans caused no warming. Greenhouse gases emitted by people held off a temperature fall that would otherwise have naturally occurred, and they caused a temperature rise on top of that.

Paris Agreement

NASA data suggest that it was 1.48°C (or 2.664°F) warmer than in 1890-1910 for the period from November 2015 to April 2016. Note again that this 1890-1910 baseline is much later than pre-industrial times. The Paris Agreement had pledged to limit the temperature rise to 1.5°C above pre-industrial levels. On land on the Northern Hemisphere, it was 1.99°C (or 3.582°F) warmer (right map of the image below).

[ Temperature anomalies for the period from November 2015 to April 2016, see also comments ]
The above images only account for a half-year period (November 2015 to April 2016), so they are only indicative for what the total rise will be for the year 2016. Nonetheless, when taking into account warming caused by people before 1900, the year 2016 looks set to hit or even exceed the guardrails that the Paris Agreement had pledged would not be crossed. The situation looks even worse when considering that temperatures measured in ice cores already included a substantial amount of warming due to humans even before the start of the Industrial Revolution.

February 2016 was 1.67°C (3°F) warmer than 1890-1910
Again, at the Paris Agreement nations pledged to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels.

When looking at a single month, February 2016 was 1.67°C (3°F) warmer than 1890-1910 (see image right). When adding a mere 0.34°C to account for warming before 1900, total warming in February 2016 did exceed 2°C. Looking at it that way, the guardrails set in Paris in December 2015 were already crossed in February 2016.


So, what is the situation? On the one hand, there's the current observed temperature rise (∆O). This rise is typically calculated as the difference between the current temperature and the temperature at a given baseline.

However, this ∆O does not reflect the full impact of human emissions. Temperatures would have been lower had there been no emissions by humans. The full warming impact due to people's greenhouse gas emissions therefore is ∆E. This ∆E is higher than the often-used observed rise, since the baseline would have been lower without warming caused by humans, i.e. including the warming that was already caused before the year 1750.

At the same time, part of global warming caused by people is currently masked due the aerosol emissions (∆M). Such aerosol emissions result mainly from burning of fossil fuel and biomass. There's no doubt that such emissions should be reduced, but the fact remains that the current temperature rise may increase substantially, say, by half when the masking effect disappears.

Thus, the full (unmasked) current warming caused by humans is the sum of these two, i.e. ∆E + ∆M, and the sum could be well over 3°C.

In addition, there is a future temperature rise that's already baked into the cake (∆F). Some feedbacks are not yet very noticeable, since some changes take time to become more manifest, such as melting of sea ice and non-linear changes due to feedbacks that are only now starting to kick in. Furthermore, the full effect of CO2 emissions reaches its peak only a decade after emission, while even with the best efforts, humans are likely to still be causing additional emissions over the coming decade. All such factors could jointly result in a temperature rise greater than ∆E + ∆M together, i.e. ∆F could alone cause a temperature rise of more than 5°C within a decade.

In summary, total anthropogenic global warming warming (∆A) or all warming caused by humans (∆E + ∆M + ∆F) could be more than 10°C (18°F) within one decade, assuming that no geoengineering will take place within a decade.

[ image added later from this post, click on images to enlarge ]

The situation is dire and calls for comprehensive and effective action as described in the Climate Plan.

[ image from ]


• Climate Plan

• Feedbacks

• Extinction

• Methane Erupting From East Siberian Arctic Shelf

• Jos Hagelaars' graph, created with graphs by Shakun et al., Marcott et al. and more, is at:

• Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation, by Shakun et al.

• A Reconstruction of Regional and Global Temperature for the Past 11,300 Years, by Marcott et al.

• The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing, by Dull et al., in:

• Arctic Climate Records Melting

• 2500 Years of European Climate Variability and Human Susceptibility, Ulf Büntgen et al. (2011)

• Paris Agreement

• February Temperature

• Defining the Anthropocene, Lewis & Maslin (2015)

• Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data, Anders Moberg et al. (2005)

• The early anthropogenic hypothesis: Challenges and responses, by W.F. Ruddiman (2007)

• Berkeley Earth, Summary Of Findings

• Reconciling divergent trends and millennial variations in Holocene temperatures, by Marsicek et al. (2018)

Reconciling divergent trends and millennial
variations in Holocene temperatures
Jeremiah Marsicek

Thursday, September 3, 2015

As 2015 smashes temperature records, it's hotter than you think

by David Spratt

Spanish version

There is an El Niño in full swing which helps push average global temperatures higher, and records are being broken, but just how hot is it? For several years, we have heard that global warming has pushed temperatures higher by around 0.8 to 0.85 degrees Celsius (°C).

But in 2015, that number is not even close.

Even before this year's strong El Niño developed, 2015 was a hot year. The first few months of the year broken records for the hottest corresponding period in previous years all the way back to the start of the instrumental record in 1880. Each month, new records fell.

With the July data in, NOAA, the US Government's National Oceanic and Atmospheric Administration, reported that July was the hottest month among the 1627 months on record since 1880, and the first seven months of the year was the hottest January-July on record:
The July average temperature across global land and ocean surfaces was 0.81°C above the 20th century average. As July is climatologically the warmest month for the year, this was also the all-time highest monthly temperature in the 1880-2015 record, at 16.61°C, surpassing the previous record set in 1998 by 0.08°C.

The July globally-averaged sea surface temperature was 0.75°C above the 20th century average. This was the highest temperature for any month in the 1880-2015 record, surpassing the previous record set in July 2014 by 0.07°C. The global value was driven by record warmth across large expanses of the Pacific and Indian Oceans.

The year-to-date temperature combined across global land and ocean surfaces was 0.85°C above the 20th century average. This was the highest for January-July in the 1880-2015 record, surpassing the previous record set in 2010 by 0.09°C.
In addition the year-to-date globally-averaged land surface temperature beat the previous record in 2007 by a whopping 0.15°C, and the year-to-date globally-averaged sea surface temperature surpassed the previous record of 2010 by 0.06°C. Every major ocean basin observed record warmth in some areas.

And, as Joe Romm has reported, "It was especially hot for the 6 billion of us up here in the northern hemisphere, where the first seven months of 2015 were a remarkable 0.3°F (0.17°C) warmer than the first seven months of any year on record — and nearly a half degree Fahrenheit warmer than any year before 2007".

El Niño may be strongest on record

So this year, records are not being broken. They are being smashed, as a strong El Niño (and perhaps the strongest on record) is set to persist through to 2016. El Niño conditions are characterised by a warm band of water across the eastern tropical Pacific Ocean and facilitate the transfer of heat from the ocean surface layer to the atmosphere and are associated with a hotter climate.

The NOAA's most recent El Niño update (Climate Prediction Center / NCEP 17 August 2015) reports that:
All multi-model averages suggest that El Niño 3.4 will be above +1.5ºC (a “strong” El Niño) during late 2015 into early 2016.
(El Niño 3.4 is the zone of longitudes 120 to 150W along the equatorial Pacific Ocean).

As the chart above illustrates, the projected strength of the El Niño (yellow line) is slightly above the previous strongest such event in 1997 (red dots).

So hot will 2015 be? The NOAA has already reported that the first seven months of the year was almost 0.1°C above the previous record. This is a huge amount in a field where changes are often measured in one-hundredths of a degree.

With a 90% chance of the El Niño persisting into 2016, it is as close as a certain bet can be that 2015 will be the hottest year on the instrumental record.

And there is probably an even-money chance that the margin will exceed 0.1°C. This would be an incredible result with scientists shocked at the margin by which records are being broken. Former NASA climate science chief James Hansen says:
We can already predict that the 2015 global temperature will exceed the prior warmest year (2014) by an unusually wide margin (~ 0.1°C), exceeding 1998 (“El Niño of the century”) even further.
And there is a good chance that 2016 will beat 2015 to become the hottest year on record.

It's hotter than you think

But much hotter has it got already? The convention is to talk about the amount of warming "above pre-industrial", that is, before the steam-and-coal industrial revolution, around 1750.

But the instrumental record used by the major agencies in the US, the UK and Japan does not start till 1880, and it is this period that is often used to provide a "pre-industrial" baseline. So when we hear that warming so far up to (the average of) the last decade as being 0.8°C or 0.85°C, it is the warming from a 1880 baseline (see light green column in figure below of 0.87°C, based on the NOAA dataset since 1880).

But the climate around 1750 and 1880 were not the same. Research using proxy data and modelling shows that between 1750 and 1880 the global average temperature increased by ~0.2°C.

 When that is added (dark green column), we find that the real warming from pre-industrial 1750 to the average of the last decade is 1.07°C. It is a shock to see that we are more than half way to the unsafe 2°C "guardrail" favoured by international policy-makers.

The warming over 1750 pre-industrial to 2014 was 1.17°C.

And for the first seven months of 2015, the margin is a staggering 1.26°C higher than the pre-industrial level. Yes, it is a strong El Niño period, and it may drop back for a short while, but 2016 could be just as hot and we may be entering a new phase of accelerated warming.

Greenhouse emissions continue to soar to record levels, and attempts to clean up and retire some of the world's dirtiest coal power plants may result in a lowering of the production of aerosols (including black-carbon soot, organic carbon, sulphates, nitrates, as well as dust from smoke, manufacturing and windstorms) which at the moment provide a temporary (~1 week) cooling of 0.8-1°C.

The leading climate researcher Michael E. Mann says that as fossil fuel use is curtailed, the aerosol cooling impact will lessen. Mann says that "if the world burns significantly less coal…we would have to limit CO2 to below roughly 405 ppm", a level we will reach in two years.

A climate emergency requiring levels of action far beyond anything that is currently perceived by policy makers? As temperatures soar to record levels and it is hotter than most people understand, you can bet on that.

Earlier posted at

As 2015 smashes temperature records, it's hotter than you think | by David Spratt

Posted by Sam Carana on Thursday, September 3, 2015