What you will find on this page – LATEST NEWS; NASA links (video); summers ARE getting hottergreenhouse gases rapidly changing atmosphere;  what is pre-industrial levelWMO climate status statement & report for 2016;  today’s extremes, tomorrow’s normal (report); Global temperature & CO2 rise from 1850 to 2016 (interactive animation); State  of the Climate 2015 Report (NOAA); climate sensitivitytipping points and temperature risewhat is IPCC up towhy do CO2 levels go up and down (video); why nights are getting warmer faster than daysglobal average temp not same everywhere;  current NOAA maps;  NASA free data set; IPCC latest reports;“97% scientist agree” (video); James Hansen speaks out (video); Two degree “safe limit”; climate system lag time;  IPCC background; IPCC latest findings 

Latest News

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End Latest News

Measuring, observing and reporting 



17 November 2014  NASA | A Year in the Life of Earth’s CO2  An ultra-high-resolution NASA computer model has given scientists a stunning new look at how carbon dioxide in the atmosphere travels around the globe……This video  is in the public domain and can be downloaded from here. Also visit NASA for the following:


NASA Global temperature change

Time Series: 1884 to 2016, image#0CLICK ON IMAGE TO ACCESS INTERACTIVE MAP: This color-coded map shows a progression of changing global surface temperatures from 1884 to 2016. Dark blue indicates areas cooler than average. Dark red indicates areas warmer than average. 

It’s Not Your Imagination. Summers Are Getting Hotter

28 July 2017, New York Times, It’s Not Your Imagination. Summers Are Getting Hotter. Extraordinarily hot summers — the kind that were virtually unheard-of in the 1950s — have become commonplace. This year’s scorching summer events, like heat waves rolling through southern Europe and temperatures nearing 130 degrees Fahrenheit in Pakistan, are part of this broader trend. The chart above, based on data from James Hansen, a retired NASA climate scientist and professor at Columbia University, shows how summer temperatures have shifted toward more extreme heat over the past several decades. To create the bell curves, Dr. Hansen and two colleagues compared actual summer temperatures for each decade since the 1980s to a fixed baseline average. During the base period, 1951 to 1980, about a third of local summer temperatures across the Northern Hemisphere were in what they called a “near average” or normal range. A third were considered cold; a third were hot. Since then, summer temperatures have shifted drastically, the researchers found. Between 2005 and 2015, two-thirds of values were in the hot category, and nearly 15 percent were in a new category: extremely hot. Practically, that means most summers are now either hot or extremely hot compared with the mid-20th century. Access interactive graphic and full article here

Greenhouse gases rapidly changing atmosphere

13 July 2017, Climate Central, Greenhouse Gases Are Rapidly Changing the Atmosphere. Humanity’s grand experiment in the atmosphere continues, and a new report documents just how far it’s gone. On Tuesday, the National Oceanic and Atmospheric Administration released its annual index of 20 key greenhouse gases. It shows that their direct influence on the climate has risen 140 percent since 1750, with 40 percent of that rise coming in just the past 26 years. That increase is almost entirely due to human activities and has caused the planet to warm 1.8°F (1°C) above pre-industrial temperatures. The index takes greenhouse gas measurements from about 80 ships and observatories around the world — gathered in all their parts per million and parts per billion glory — and boils them down into a simple numerical index, which defines the rise from 1700-1990 as 100 percent or simply 1. This year’s number: 1.4. It’s a simple number that contains multitudes. For example, carbon dioxide’s influence on the climate has increased 54 percent overall since 1990. The four other major greenhouse gases in the index, which include nitrous oxide, methane and two types of chlorofluorocarbons, are responsible for 42 percent of the increase with 15 minor greenhouse gases accounting for the missing 4 percent. Carbon dioxide has risen rapidly in the atmosphere, with 2016 marking the second-largest annual increase ever observed at the Mauna Loa Observatory, the world’s main measuring station. This May, monthly carbon dioxide peaked at 409.65 parts per million. That’s a record high and a mark unseen in human history. If emissions continue on their current trend, the atmosphere will hit a state unseen in 50 million years. A bright spot in the report is the decline of chlorofluorocarbons’ warming influence on the planet. The chemicals were commonly used as refrigerants until the Montreal Protocol banned them in 1989. The treaty came about because they deplete the protective ozone layer, but phasing them out has also helped reduce their warming impact on the climate. Read More here  (GRAPH: Radiative forcing, relative to 1750, of all the long-lived greenhouse gases. The NOAA annual greenhouse gas index, which is indexed to 1 for the year 1990, is shown on the right axis.Credit: NOAA)

What does pre-industrial levels mean?

8 June 2017, The Conversation, What is a pre-industrial climate and why does it matter? Over the past few days there has been a lot of talk about the Paris climate agreement, from which the United States is planning to withdraw. Although this is a setback, there is still near-complete consensus from the world’s governments that a strong effort to tackle climate change is needed. The Paris Agreement aims to limit global warming relative to a pre-industrial baseline. Its precise commitment is: Holding the increase in the global average temperature to well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃ above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change. But this begs the question: what are “pre-industrial levels”? Clearly, if we’re aiming to limit global warming to 1.5℃ or 2℃ above a certain point, we need a common understanding of what we’re working from. But the Paris Agreement doesn’t provide a definition. This becomes key as governments expect climate scientists to coherently compare different plans to reach their Paris targets. It’s crucial to be clear on what researchers mean when we say “pre-industrial”, and what assumptions our projections are based on. Of course, as the chart below shows, no matter which baseline we use it’s clear there’s been a drastic rise in global temperature over the last century. Read More here

Provisional WMO Statement on the Status of the Global Climate in 2016

14 November 2016: 2016 is set to break even the temperature records of 2015. It is very likely that 2016 will be the hottest year on record, with global temperatures even higher than the record-breaking temperatures in 2015. Preliminary data shows that 2016’s global temperatures are approximately 1.2° Celsius above pre-industrial levels, according to an assessment by the World Meteorological Organization (WMO). Global temperatures for January to September 2016 have been about 0.88° Celsius (1.58°F) above the average (14°C) for the 1961-1990 reference period, which is used by WMO as a baseline. Temperatures spiked in the early months of the year because of the powerful El Niño event of 2015-16. Preliminary data for October indicate that they are at a sufficiently high level for 2016 to remain on track for the title of hottest year on record. This would mean that 16 of the 17 hottest years on record have been this century (1998 was the other one).

Access Provisional Statement here. Access full WMO report here



Today’s extremes, tomorrow’s normal

7 November 2016, The Conversation. The recent record-breaking temperatures have often been described as the “new normal”. For example, after the new global temperature record was set in 2016, these high temperatures were described as a new normal. What is a new normal for our climate? The term has been used broadly in the media and in scientific literature to make sense of climate change. Put simply, we should get used to extremes temperatures, because our future will be extreme. 

Extreme heat events increasing

But without a precise definition, a new normal is limited and difficult to understand. If 2015 was a new normal for global temperatures, what does it mean if 2017, 2018, or 2019 are cooler? In our study we defined the new normal as the point in time when at least half the following 20 years are warmer than 2015’s record breaking global temperatures. We examined extreme temperatures in a number of state-of-the-art climate models from an international scientific initiative. We also explored how different future greenhouse gas emissions impact temperatures.  We used four different greenhouse gas scenarios, known as Representative Concentration Pathways, or RCPs. These range from a business-as-usual situation (RCP8.5) to a major cut to emissions (RCP2.6). It is worth emphasising that real-world emissions are tracking above those covered by these hypothetical storylines.

Future extremes: Our findings were straightforward. 2015’s record-breaking temperatures will be the new normal between 2020 and 2030 according to most of the climate models we analysed. We expect within a decade or so that 2015’s record temperatures will likely be average or cooler than average.

By 2040, 2015’s temperatures were average or cooler than average in 90% of the models. This result was unaffected by reducing greenhouse gas emissions or not – we are already locked in to a significant amount of further warming. Read More here Access full AMERICAN METEOROLOGICAL SOCIETY Report here

Interactive animation of monthly global surface temperatures from 1850 to 2016

14 December 2016, MET UK: Explore their interactive animation of monthly global surface temperatures from 1850 to 2016, and some of the key events that have influenced this 166-year-long record. This interactive animation is a collaboration between the Met Office Informatics Lab and the Met Office Hadley Centre. NOTE: Click on graphic to access animation, when open click and hold on globe to view different parts of the globe. 

State of the Climate 2015 Report

stateofclimate2015_cover2 August 2016: An international, peer-reviewed publication released each summer, the State of the Climate is the authoritative annual summary of the global climate published as a supplement to the Bulletin of the American Meteorological Society. The report, compiled by NOAA’s Center for Weather and Climate at the National Centers for Environmental Information is based on contributions from scientists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instruments located on land, water, ice, and in space. Access Report here

2 August 2016, Carbon Brief, Scientists confirm multiple climate records broken in 2015. Last year saw records in the Earth’s climate system continue to tumble, says the latest State of the Climate report from the US National Oceanic and Atmospheric Administration (NOAA). The 300-page report, now in its 26th year, is an annual assessment of the world’s climate, scrutinising the Earth’s land, oceans, ice and atmosphere. It is compiled by more than 450 scientists from 62 countries. Carbon Brief takes a look at how rising greenhouse gas emissions, with the help of a strong El Niño event, made 2015 into a record-breaker. Greenhouse gases Last year was record-breaking for concentrations of all three of the main long-lived greenhouse gases that contribute to climate change: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). At the Mauna Loa Observatory, where scientists have been monitoring CO2 since the 1950s, the average concentration for the year as a whole surpassed 400 parts per million (ppm) for the first time. At 400.8ppm, CO2 levels in the atmosphere were 3.1ppm greater than 2014 – the largest annual increase of the 58-year record. In addition, March 2015 was the first time average CO2 concentration across the globe has been more than 400ppm for an entire month. Global annual average CO2 levels for 2015 finished just shy of the 400ppm milestone, at 399.4 ppm. You can see this in the chart below, one of several graphics produced alongside the report. Meanwhile, levels of both methane and nitrous oxides reached new record highs in 2015, at 1834.0 parts per billion (ppb) and 328.2ppb, respectively. Read More here

Top: Average surface temperatures for 2015, against a baseline of 1981-2010. Shading indicates where temperatures are above (red) or below (blue) average. Bottom: Global temperature since 1880 for the surface (dark red line) and the troposphere (pale red line), against a baseline of 1981-2010


Scientists find common ground over climate sensitivity. 

oceanheatadjustedocean28 June 2016, Carbon Brief, A new paper helps to shed light on one of the biggest questions in climate science: how much the climate will warm in future? The answer to this depends a lot on something scientists call the “climate sensitivity” – a measure of how much the climate warms in response to greenhouse gases. Until now, scientists have been grappling with how to reconcile the fact that different ways to estimate the climate sensitivity have, so far, come up with quite different answers. This uncertainty has never been a reason to question whether climate change will be serious or to delay action to tackle emissions, though it has often be misused by climate skeptics this way. But a question mark over the value of climate sensitivity has meant that projections of future temperature rise are less precise than scientists would like. It also makes it harder to gauge our chances of staying below a given temperature limit, such as 2C above pre-industrial levels. A new paper published in Nature Climate Change says there is, in fact, no disagreement between the different methods after all. In reality, they measure different things and once you correct for the fact that the historical temperature record underestimates past warming, the gap closes. The implications are significant since it suggests we’ve seen around 0.2C more warming than previously thought, says co-author Dr Ed Hawkins in his Climate Lab Book blog. Read More here

This chart perfectly explains what’s at stake in the quest to stop climate change

climate triggers graph23 June 2016, Washington Post: Here at the Energy and Environment blog, we cover, regularly, the tipping points of climate change — how, for instance, the glaciers of West Antarctica may already have passed a key threshold that leads to unstoppable melt. We cover the history of the Earth’s climate — including why the Holocene era, which began some 11,700 years ago and we lived in up until fairly recently (when many researchers believe an “Anthropocene” began), was so stable and conducive to human civilization. And of course we cover the quest to keep warming below the Paris climate targets, 1.5 degrees and 2 degrees Celsius, and the scenarios for greenhouse gas emissions that might be capable of doing that — and also those that can’t. [The math the planet relies on isn’t adding up right nowBut these are all complicated, nuanced stories, and the idea that they can all be pulled together into one analysis — much less one figure — is hard to believe. Nonetheless, I think three researchers from the Potsdam Institute for Climate Impact Research have done precisely that with the image below, which is part of an optimistic essay they just published in Nature Climate Change, suggesting that the recently negotiated Paris climate agreement has what it takes to stabilize climate change. In the process, the researchers deliver the sort of rare big picture analysis that we mortals need now and again to understand why scientists are generally so freaked about a warming climate, and also why, in this case, they’re feeling a shard of hope. 

Click on image above to enlarge, with unpacking following: Schellnhuber et al., Nature Climate Change. The figure shows, according to the authors, the “global mean surface temperature evolution from the Last Glacial maximum through the Holocene,” combined with the temperature range aspired to in the Paris climate agreement, possible temperature rises for different greenhouse gas emissions scenarios (RCP2.6, RCP8.5, and so on), and the tipping point thresholds for various major planetary changes. Access full article here

What is IPCC up to?

At its 43rd Session (Nairobi, Kenya, 11 – 13 April 2016), the IPCC Panel decided to prepare a special report on climate change and the oceans and the cryosphere. The Special Report will be developed under the joint scientific leadership of Working Groups I, II and III with support from the WGII TSU. The report will be finalized in September 2019. The meeting to produce the draft outline for the Special Report was held on 6 – 9 December 2016 in Monaco. The Panel will consider the draft outline during its next Session at the end of March 2017. 

IPCC AR6 Working Group Reports due:

  • Working Group 1 (assesses the physical scientific aspects of the climate system and climate change. The main topics assessed by WG I include: changes in greenhouse gases and aerosols in the atmosphere; observed changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets, oceans and sea level; historical and paleoclimatic perspective on climate change; biogeochemistry, carbon cycle, gases and aerosols; satellite data and other data; climate models; climate projections, causes and attribution of climate change. ): April 2021
  • Working Group 2 (assesses the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change, and options for adapting to it. It also takes into consideration the inter-relationship between vulnerability, adaptation and sustainable development): October 2021
  • Working Group 3 (assesses options for mitigating climate change through limiting or preventing greenhouse gas emissions and enhancing activities that remove them from the atmosphere. The main economic sectors are taken into account, both in a near-term and in a long-term perspective): July 2021


FINAL IPCC Synthesis Report – AR6 approved 4-10 April 2022. For more information access here

Yet another way to visualise temperature rise – How many do we need?

Spiral temp graphicThe animated spiral presents global temperature change in a visually appealing and straightforward way. The pace of change is immediately obvious, especially over the past few decades. The relationship between current global temperatures and the internationally discussed target limits are also clear without much complex interpretation needed. Click on graphic to go to animated spiral.

Data: HadCRUT4.4 from January 1850 – March 2016, relative to the mean of 1850-1900, available here

1. Features you can see:
1877-78: strong El Nino event warms global temperatures
1880s-1910: small cooling, partially due to volcanic eruptions
1910-1940s: warming, partially due to recovery from volcanic eruptions, small increase in solar output and natural variability
1950s-1970s: fairly flat temperatures as cooling sulphate aerosols mask the greenhouse gas warming
1980-now: strong warming, with temperatures pushed higher in 1998 and 2016 due to strong El Nino events

2. Why start in 1850? Because that is when the HadCRUT4 dataset starts, as we don’t have enough temperature data before then to reliably construct global average temperature

3. Are temperatures ‘spiralling out of control’? No. Humans are largely responsible for past warming so we have control over what happens next.

4. What do the colours mean? The colours represent time. Purple for early years, through blue, green to yellow for most recent years. The colour scale used is called ‘viridis’ and the graphics were made in MATLAB.

Source: Climate Lab Book

21 January 2016, NASA, NOAA Analyses Reveal Record-Shattering Global Warm Temperatures in 2015

The planet’s average surface temperature has risen about 1.8 degrees Fahrenheit (1.0 degree Celsius) since the late-19th century,

Earth’s 2015 surface temperatures were the warmest since modern record keeping began in 1880, according to independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA). Globally-averaged temperatures in 2015 shattered the previous mark set in 2014 by 0.23 degrees Fahrenheit (0.13 Celsius). Only once before, in 1998, has the new record been greater than the old record by this much……The planet’s average surface temperature has risen about 1.8 degrees Fahrenheit (1.0 degree Celsius) since the late-19th century, a change largely driven by increased carbon dioxide and other human-made emissions into the atmosphere. Access data here and NOAA/NASA Annual Global Analysis for 2015 here


CO2 increasing but why do the levels go up and down?

15 May 2015, Climate Central: The reason that CO2 is building up to higher levels each year is related to the seasonal cycle. While plants take up CO2 as they awaken after their winter hibernation, and then release it again as they go dormant again in the fall, they can only sop up so much in a given season, leaving behind an ever-growing excess amount. Climbing CO2 peak Climate Central

Right now, that excess is to the tune of about an extra 2 ppm accumulating in the atmosphere every year. That means that the CO2 peak that comes each May is around 2 ppm higher than it was the year before, as shown in the graph below. This year, that peak is expected to be around 405 ppm. But not only is the amount of CO2 in the atmosphere going up every year, the amount by which it is doing so is accelerating; back in the 1950s, the yearly increase was only about 0.75 ppm per year. The rate of that acceleration is a factor of human CO2 emissions, 



Global average carbon dioxide concentrations as seen by NASA’s Orbiting Carbon Observatory-2 mission, June 1-15, 2015. OCO-2 measures carbon dioxide from the top of Earth’s atmosphere to its surface. Higher carbon dioxide concentrations are in red, with lower concentrations in yellows and greens. Credit: NASA/JPL-Caltech

29 October 2015, NASA Global Climate Change, Armed with a full annual cycle of data, OCO-2 scientists are now beginning to study the net sources of carbon dioxide as well as their “sinks” — places in the Earth system that store carbon, such as the ocean and plants on land. This information will help scientists better understand the natural processes currently absorbing more than half the carbon dioxide emitted into the atmosphere by human activities. This is a key to understanding how Earth’s climate may change in the future as greenhouse gas concentrations increase. Read More here

Why are nights heating up faster than days?

10 March 2016, Bjerknes Centre, Observations from the last fifty years have shown that the nights have been warming much faster than the days. Analysis of the causes of this more rapid warming at night shows that this is likely to continue in the coming decades. A new publication led by Richard Davy, researcher at the Nansen Centre and the Bjerknes Centre has examined the causes of the more rapid warming at night compared to the day, which has been seen around the globe in recent decades. They have analysed the causes of these changes from observations and model reconstructions of the climate in the 20th century. By using model reconstructions they were able to determine how much of this asymmetrical warming could be explained by different processes. Past efforts to understand the reason for this enhanced warming have focused on changes to climate processes that may have occurred at this time, such as increases in cloud cover, precipitation or soil moisture content. However, Davy and colleagues have shown that part of this more rapid warming at night is innate to the climate system, because the night-time temperatures are inherently more sensitive to climate forcing. 

Cartoon on the boundary-layer day and night by Richard Davy.

(Cartoon on the diurnal cycle by Richard Davy)

The layer of air just above the ground is known as the boundary-layer, and it is essentially separated from the rest of the atmosphere. At night this layer is very thin, just a few hundred meters, whereas during the day it grows up to a few kilometres. It is this cycle in the boundary-layer depth which makes the night-time temperatures more sensitive to warming than the day. The build-up of carbon dioxide in the atmosphere from human emissions reduces the amount of radiation released into space, which increases both the night-time and day-time temperatures. However, because at night there is a much smaller volume of air that gets warmed, the extra energy added to the climate system from carbon dioxide leads to a greater warming at night than during the day. Read More here

How a global average of 2oC does not mean its the same temp rise everywhere 

20 January 2016, Eureka Alert (Uni NSW) How a 2°C rise means even higher temperatures where we live. Land based temperatures rise much faster than global average temperatures



Regions around the Arctic may have passed a 2°C temperature rise as far back as 2000 and, if emissions rates don’t change, areas around the Mediterranean, central Brazil and the contiguous United States could see 2°C of warming by 2030. This is despite the fact that under a business as usual scenario the world is not expected to see global average temperatures rise by 2°C compared to preindustrial times until the 2040s. New research published in Nature led by Prof Sonia Seneviratne from ETH Zurich with researchers from Australia’s ARC Centre of Excellence for Climate System Science (ARCCSS) has quantified the change in regional extremes in a world where global average temperatures have risen by 2°C. The research shows worldwide warming extremes over land generally exceed the rise in this scenario, in some cases by as much as 6°C. “We even see starkly different rates of extreme warming over land even when global average temperatures reach just 1.5°C, which is the limit to the rate of warming agreed to at the Paris talks,” said lead author Prof Seneviratne. “At 1.5°C we would still see temperature extremes in the Arctic rise by 4.4°C and a 2.2°C warming of extremes around the Mediterranean basin.” The extreme regional warming projected for Alaska, Canada, Northern Europe, Russia and Greenland could have global impacts, accelerating the pace of sea-level rise and increasing the likelihood of methane releases prompted by the melting of ice and permafrost regions. Read More here

NOAA Global Temperature and Precipitation Maps

NOAA july temp map

NOAA july prec map

NOAA july extreme events

For more maps and data go to NOAA’s site here

29 July 2015, The Carbon Brief Updated: The climate change papers most featured in the media

Top climate papersIn our recent series on the top climate change papers, we brought you which ones scientists think are the most influential and which are the most cited by other researchers. With the help of Altmetric, we also looked into which research articles have made the biggest splash in the news and on social media. But, as a few eagle-eyed readers pointed out to us, it seems there were some papers that were overlooked. Altmetric has now expanded their search to make sure no paper is missed. So here’s our revised take on which papers have made the biggest impact in the wider world. Read More here


NASA’s New Climate Projections, Now On the Cloud

12 June 2015, NASA RELEASE: NASA has put a new item up on Amazon. But there’s no price tag and you won’t necessarily find it by using the marketplace’s search bar or browsing the electronics section. Instead, you’ll have to look at Amazon’s cloud, where NASA scientists have shared 11 terabytes of high resolution climate projections. A snapshot of July in 2100 in the map below shows how detailed the projections are (global high temperatures in July 2100 under high greenhouse emissions). The new dataset is available to anyone with an internet connection, but comes courtesy of supercomputers only available to NASA scientists and a lucky handful of grantees. If you want to access the data set go here.


Access IPCC’s AR5 reports


Where did the “97%” of climate scientist agree with man-made global warming” come from?

15 May 2013, IOP Science

For full transcript access link here

What makes a climate scientist take to the streets

Top climate scientist James Hansen tells the story of his involvement in the science of and debate over global climate change. In doing so he outlines the overwhelming evidence that change is happening and why that makes him deeply worried about the future.

Source: Ted Talks

Hansen causing controversy over new report published prior to being peer reviewed

23 July 2015, Washington Post, It has been widely discussed — but not yet peer reviewed. Now, though, you can at least read it for yourself and see what you think. A lengthy, ambitious, and already contested paper by longtime NASA climate scientist James Hansen and 16 colleagues appeared online Thursday in Atmospheric Chemistry and Physics Discussion, an open-access journal published by the European Geosciences Union. The paper, entitled “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ◦C global warming is highly dangerous” is now open for comment — peer review in this journal happens in public. And given how much attention the work has already received, it’s likely to generate plenty of comments from fellow scientists. Read More here. Access full report here

15 December 2015, YALE Climate Connections: James Hansen Calls Out ‘Baloney’ on COP21 Climate Progress. Citing climate ’emergency,’ the scientist-turned activist is unimpressed with COP21 outcome, opts for nuclear – but not carbon capture and sequestration – in ‘all hands on deck’ approach…..“We really have an emergency because of the inertia of the system,” Hansen said – or, as his grandson put it, unless we have a time machine, we can’t fix much of the climate change happening now and in the future. “A solution is possible, and economic[ally] sensible, and it’s not been being advocated by any nation,” said Hansen, who expressed frustration about the outcome of the recent COP21 climate conference in Paris. He said the idea that the world is “making good progress” is “baloney.” Hansen’s preferred solution is a carbon fee-and-dividend, with all collected fees (taxes) distributed back on an equal per capita basis. Such a system has been backed also by groups such as the Citizens Climate Lobby. Read more here


Two Degrees “safe limit” and why did they pick it?

8 December 2014, Carbon Brief, Two degrees: The history of climate change’s ‘speed limit’: Limiting warming to no more than two degrees has become the de facto target for global climate policy. But there are serious questions about whether policymakers can keep temperature rise below the limit, and what happens if they don’t. As climate negotiators meet in Lima to discuss a new global climate deal that could limit warming to two degrees or less, we look at each of the issues in turn. Here, we take a look at where the two degree target came from, and how it has ended up guiding international climate policy. Read More here
2 degree history

And is this a sensible way to decide what is “safe”?

15 June 2015, The Carbon Brief an In-depth analysis: Is the 1.5C global warming goal politically possible? For the past five years, international climate change negotiations have been guided by the principle that the rise in global average temperatures should be limited to “below 2C above pre-industrial levels”. Is this goal adequate? Probably not, according to a report conducted by the UN and launched at the climate change negotiations in Bonn. Containing the views of 70 scientists gathered together in a process called the ” structured expert dialogue” (SED), the report warns that even current levels of global warming – around 0.85C – are already intolerable in some parts of the world. It says: “Some experts warned that current levels of warming are already causing impacts beyond the current adaptive capacity of many people, and that there would be significant residual impacts even with 1.5C of warming (e.g. for sub-Saharan farmers), emphasising that reducing the limit to 1.5C would be nonetheless preferable.” This report provides the evidence base for discussions at UN level over whether the world is being ambitious enough on long-term action to tackle climate change.

The main finding of the SED report is that the 2°C limit is indeed too warm for many vulnerable systems and regions, and a 1.5°C limit would be significantly safer. In addition, the SED advises that 2°C should not be seen as a guardrail, but rather a defence line, that should not be crossed. And if we want to be sure not to cross it, we should actually aim for a 1.5°C limit.

And perhaps one of the most important implications in the short term of the SED findings is its advice to “avoid embarking on a pathway that unnecessarily excludes a warming limit below 2 °C.” These results confirm the views of the most vulnerable groups, like the SIDS and LDCs, who have pushed for a 1.5°C limit since the Copenhagen meeting. The report underscores the scientific legitimacy and significance of their case. It is now important that these findings make their way into the negotiations on the new global agreement now underway and scheduled to conclude in Paris in December 2015. You can read Climate Analytics’ briefing on the main points covered by the SED here.

Climate talks in Bonn: While the message of the report is clear, it does not close the current chasm between climate science and policy. At UN climate negotiations in Bonn last week, the report and its findings were subject to intense scrutiny and discussion by diplomats from around the world. It is these policymakers – not the scientists – who get the final say on whether the findings become the new basis for future political decisions, embedded in a new international climate deal set to be signed at the end of this year in Paris.

The views of diplomats around the world differ widely on how the findings of the report should be incorporated. At the most hopeful end of the scale, countries want to include an official decision that “there is a need to strengthen the global goal on the basis of limiting warming to below 1.5C above pre-industrial levels”. A minority would rather ignore the report – the product of two years’ work – altogether. In any case, two weeks of discussions ended in an outcome that most had hoped to avoid: just two short sentences acknowledging that a report had been written, and that countries would continue to discuss it when they meet again in Paris. Read More here 

27 May 2015, The Conversation, A matter of degrees: why 2C warming is officially unsafe: The goal of international climate negotiations is “to avoid dangerous atmospheric concentrations of greenhouse gases”. In 2010, Parties to the United Nations Framework Convention on Climate Change formally recognised the “long term goal” of the convention was to hold the increase in global average warming to below 2C above pre-industrial levels. Is 2C therefore the safe limit above which climate change becomes “dangerous”? A UN expert dialogue of more than 70 scientists, experts, and climate negotiators recently released a final report concluding that 2C is “inadequate” as a safe limitRead More here. View the full UN Report here. If you want just the basics scroll through to the message boxes. 

05 May 2015, Climate Code Red: Hansen says “It’s crazy to think that 2 degrees Celsius is safe limit”…..Then there is the world of international policy-making, where the talk is of trying to keep warming to 2°C, when in fact the current level of commitments in the lead up to the Paris talks looks like normalising policies consistent with 3°C of warming. Today Fairfax media reported Lord Stern as recognising that the Paris commitments “would be like a path upwards of 3°C on the basis of current intentions… We haven’t been there for three million years and we haven’t been at four degrees for tens of millions of years.” Also today, the world’s most well-known and certainly one of the greatest climate scientists, James Hansen, told ABC Radio National Breakfast that “its crazy to think that 2 degrees Celsius is safe limit.” Read More here

The slow response (lag time) of the climate system

Figure 2.6 below shows estimates of the time it takes for different parts of the climate system to respond to a situation where emissions are reduced to equal the rate of natural removal. While greenhouse gas concentrations stabilise in around a hundred years, the temperature and sea-level rise due to thermal expansion of the oceans takes much longer to stabilise. The melting of ice sheets is still increasing the sea level even after a thousand years.

Figure 2.6 Inertia in the climate system

Figure 2.6

Source: IPCC (2001b: Figure 5.2), reformatted for this publication.

 Also go to “All things carbon and emissions” page on this site for related information


Intergovernmental Panel on Climate Change (IPCC)

 The IPCC is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate related data or parameters. 

The IPCC produces regular Assessment Reports. In 1990 their first report (AR1) was produced. The latest report the Fifth Assessment Report (AR5) has been completed, with the final Synthesis Report (SYR), which integrates and synthesises material from the three Working Group reports into a summary for policymakers was finalised on 31 October 2014.

The three working groups of IPCC are:

  • Working Group I (WG I) assesses the physical scientific aspects of the climate system and climate change
  • Working Group II (WG II) assesses the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change, and options for adapting to it.
  • Working Group III (WG III) assesses options for mitigating climate change through limiting or preventing greenhouse gas emissions and enhancing activities that remove them from the atmosphere.


Three things you need to keep in mind when reading IPCC Reports

1. Who signs off on the final reports

Each Summary for Policymakers is written by a team of scientists and reviewed by experts and government representatives as part of the second draft of the Working Group report. Government representatives then meet and negotiate an agreement of the final wording line by line. This process is intended to result in language that can be understood by policymakers and to increase the chance that governments will ‘buy in’ to the key conclusions of the assessment.

This however raises concerns that reinterpretation of the assessment’s findings, suggested in the final Plenary might be politically motivated. As these negotiations can also take several days and commonly end in an all night session it can give the impression that individuals with the most endurance or the countries that have large delegations can end up having the most influence on the report. Source: Evaluation of IPCC’s Assessment Process. 

It is therefore best to consider the findings from IPCC Assessment Reports as conservative.

2. IPCC Scenarios

A place where the non-scientific person can flounder in ignorance and boredom. But knowing the basics is essential in understanding what the science is saying. The AR5 bases its findings on a new set of scenarios that replace the Special Report on Emissions Scenarios (SRES) standards employed in the two previous reports.  The new scenarios are called Representative Concentration Pathways (RCPs). There are four pathways: RCP8.5, RCP6, RCP4.5 and RCP2.6 – the last is also referred to as RCP3-PD. (The numbers refer to forcings for each RCP; PD stands for ‘Peak and Decline).

The IPCC Scenario Process for AR5 states: “The goal of working with scenarios is not to predict the future but to better understand uncertainties and alternative futures, in order to consider how robust different decisions or options may be under a wide range of possible futures”.

Representative Concentration Pathways (RCPs) Primary Characteristics

RCP 8.5 Increasing greenhouse gas emissions over time, representative of scenarios in the literature that lead to high greenhouse gas concentration levels (Riahi et al. 2007)

RCP 6 Stabilisation scenario in which total radiative forcing is stabilised shortly after 2100, without overshoot, by the application of a range of technologies and strategies for reducing greenhouse gas emissions (Fujino et al. 2006; Hijioka et al. 2008).

RCP 4.5 Stabilisation scenario in which total radiative forcing is stabilised shortly after 2100, without overshooting the long-run radiative forcing target level (Clarke et al. 2007; Smith and Wigley 2006; Wise et al. 2009).

RCP 2.6 Representative of scenarios in the literature that lead to very low greenhouse gas concentration levels; It is a “peak-and-decline”  scenario; In order to reach the specific radiative forcing levels, greenhouse gas emissions (and indirectly emissions of air pollutants) are reduced substantially, over time. (van Vuuren et.al. 2011)

If you are now totally confused either go to the following links for more detail:

The Beginners Guide to Representative Concentration Pathways;

Scenario Process for AR5 

or REMEMBER when you are reading any scientific reports using these scenarios the world is currently tracking at the highest emission rate scenario RCP 8.5.

3. The language - IPCC Likelihood Probability Scale (Likelihood of the Outcome) and Confidence Levels

 When the IPCC scientists use the terms ‘confidence’ and ‘likelihood,’ each term has a different and very specific meaning relating to levels of certainty.

When scientists mention ‘confidence’, they are referring to the degree of confidence in being correct. In the case of the IPCC where scientists are analysing global climate, issues such as lack of observational data in certain regions, such as Africa, will affect scientists’ confidence in their findings. When scientists mention ‘likelihood’ they are referring to the probability of an event or outcome occurring.

If an event is given a very high confidence level, there is a combination of high agreement and robust evidence that it will occur.


Term Likelihood of the outcome
Virtually certain >99% probability
Extremely likely >95% probability
Very likely >90% probability
Likely >66% probability
More likely than not >50% probability
About as likely as not 33 to 66% probability
Unlikely <33% probability
Extremely unlikely <5% probability
Exceptionally unlikely <1% probability

If an event is virtually certain, there is a greater than 99% probability that it will occur.

REMEMBER: When you read IPCC reports and see these terms have a think about the probability rating of ordinary activities that we all normally insure against:

  • House burning down: 1% probability
  • Involved in serious car accident in our lifetime: 30% probability
  • And the days we buy a lottery ticket, just in case…: 0.026084% probability of winning (less than 3/100th of a percent)


You would think it’s a no brainer to put into place some proactive risk management when faced with the odds above.

Sources:  Confidence and Likelihood in the IPCC Fifth Assessment Report Fact Sheet, Australian Govt, Dept of Environment

IPCC Cross-Working Group Meeting on Consistent Treatment of Uncertainties

End Section


Key messages Fifth Assessment Report (AR5)

Greenhouse gas concentrations not seen for 800,000 years

The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

Human influence on the climate system is clear

This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system. It is extremely likely (95-100% probability) that human influence has been the dominant cause of the observed warming since the mid-20th century.

Warming will continue

Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions. Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform.

Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2.

Observed changes are unprecedented

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. Continuing changes include:

….very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century…global glacier volume will further decrease.

….global mean sea level will continue to rise during the 21st century. Under all RCP scenarios, the rate of sea level rise will very likely exceed that observed during 1971 to 2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.

….continuing uptake of carbon by the ocean will increase ocean acidification.

very likely that heat waves will occur with a higher frequency and duration

…extreme precipitation events over most of the mid-latitude land masses and over wet tropical regions will very likely become more intense and more frequent by the end of this century