Archive for the ‘Issue 225’ Category

Dangerous Climate Change – How Close Are We?

Posted by Ken on October 22, 2017
Posted under Issue 225

Dangerous Climate Change – How Close Are We?

Monthly Climate Update:  August 2017


Jeff Obbard, Ph.D.*

*Jeff is a Professor of Environmental Science, currently based at Qatar University. He was previously based at the National University of Singapore, where he served as Director for the Sustainable Development & Water Alliance, and as Research Director for the Tropical Marine Science Institute. He has been identified in Singapore as a Top 100 Global Sustainability Leader, and is a recipient of the United Nations Mondialogo Award on sustainable development. Jeff was an invited Expert Reviewer for the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.


This column is the start of a new series in ABC Carbon which provides monthly update on the latest climate data pertaining to measurements of average mean global surface temperatures (AMGST), and the prevailing atmospheric concentrations of the main greenhouse gases i.e. carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

Data is sourced from instrumental records (not computer models), as reported by the National Oceanic & Atmospheric Administration (NOAA), the Goddard Institute of Space Studies (GISS) of the National Aeronautical and Space Administration (NASA), the Earth System Research Laboratory (ESRL), and the Earth Institute at Columbia University, USA – and elsewhere, as appropriate.

As well, as providing information on climate data trends, this first column puts the data into the context of climate change policy with respect to the Paris Climate Agreement (PCA), which entered into force on 4 November 2016. The central goal of the PCA is to limit AMGST rise this century to below
two degrees centigrade (2oC) above pre-industrial levels, and to pursue efforts to limit the increase to no more than 1.5oC.  Reference is also given to the 1992 United Nations Framework Convention on Climate Change (UNFCC), where nations agreed to reduce GHG emissions so as to prevent ‘dangerous’ anthropogenic (human) interference with the Earth’s climate system.

The graph below shows recent monthly mean CO2 concentrations, as measured at the ESRL at Mauna Loa, Hawaii. The last four complete years of the Mauna Loa CO2 data set, plus the current year (2017) are shown.

Note: In the figure, the dashed red line with diamond symbols represents the monthly mean values, centred on the middle of each month. The black line with the square symbols represents the same, after correction for the average seasonal cycle.

The average atmospheric CO2 concentration for August 2017 (as released by NOAA on 11 September) was 405.07 parts per million (ppm). This compares to 402.25 ppm in August 2016, an annual increase of 2.82 ppm.  The annual rate of increase of CO2 in the atmosphere 10 years ago (2007) was 2.27 ppm, and 20 years ago (1997) was 1.93 ppm indicating that the rate of accumulation of CO2 in the atmosphere is accelerating.

August 2017 was the second warmest August on record since reliable measurements began in 1880 at+ 0.85C warmer than a 1951-1980 average baseline temperature.  August 2016 was the warmest August ever recorded   at +0.99C. Although it is still too early to rank the 2017 as a whole, 2016 AMGST was +1.24oC  above a 1880-1920 average baseline, and was the warmest year on the instrumental record (see Figure 1).  In terms of a global warming trend, then 2015 was the second warmest year on record and 2014 the third, where 16 of the last 17 warmest years on record have all occurred in the 21st century.

Figure 1: Average mean global surface temperature relative to 1880-1920 mean

Source:  Goddard Institute of Space Studies, NASA.

CO2 is the main GHG associated with fossil-fuel combustion and global warming, and also the most long-lived in the atmosphere with a residence time measured in decades to centuries. The other main GHGs found in the atmosphere, apart from short-lived water vapour, include: methane (CH4) which has a global warming potential (GWP) relative of about 32 times stronger than CO2 (over 100 years) but a shorter atmospheric residence time of about 10 years, and; nitrous oxide (N2O) which has a GWP of about 280 times stronger than CO2 and an atmospheric residence time of over 100 years.

CH4 and N20, although potent GHGs, occur at much lower atmospheric concentrations than CO2 – but both are now present at elevated concentrations relative to pre-industrial times. The concentration of CH4 in the atmosphere in June 2017 (last updated by NOAA on 05 September) was 1843.4 parts per billion (ppb), versus 1837 ppb in June 2016. This compares to less than 900 ppb of atmospheric CH4 in pre-industrial times i.e. an increase of over 100%.  Atmospheric N20 concentrations are are now about 330ppb versus 273 ppb for pre-industrial  times i.e. an increase of over 20%. By combining the contribution of all GHGs to atmospheric warming and then expressing it as an equivalent CO2 concentration, then latest available data set for atmospheric GHGs (NOAA, ESRL 2016) indicates a CO2 equivalent (CO2e) GHG concentration in the atmosphere of 489ppm CO2e – i.e. in excess of the 450 ppm CO2e associated with capping AMGST to 2oC by 2100 (50% probability).

Based on the best linear fit of decadal AMGST of 0.17oC per decade (1970-2017 data, see Figure 2), and a conservative assumption that the rate of increase remains constant going forward, then the 1,50C limit of the PCA can be expected to be breached in about 15 years’ time i.e. 2032 and the 2oC limit in about 45 years’ time i.e. 2062.  Current national pledges to reduce carbon emissions under the PCA indicate that the National Determined Contributions (NDCs), as submitted by signatory nations to the agreement will, according to the International Energy Agency, result in an AMGST increase of 2.7oC by the year 2100, and 3oC thereafter.

These estimates do not include the denigration of the integrity of the PCA, as prompted by the decision, in June 2017, of the USA, the world’s second largest emitter of CO2 to atmosphere, to withdraw from the agreement.  Further, climate sensitivity data i.e. the measure of the response of the global climate system to a given radiative forcing by atmospheric GHGs, coupled with paleoclimate (earth history) evidence, suggest that current levels of AMGST warming i.e. +1.28oC are sufficient to trigger long-term positive feedbacks in the climate system and accelerate global warming. Such feedbacks include the disintegration of the world’s ice-sheets, and the melting of carbon-rich Arctic permafrost. Indeed, paleoclimate data from the Eemian interglacial period, from about 126,000 years ago indicates that equilibrium AMGST for similar atmospheric GHG concentrations in the atmosphere that we see today resulted in sea levels between 6 and 9 metres higher than present.

Although the physics of climate change is not in question scientifically, the time taken to reach radiative equilibrium for an energy imbalance in the earth-atmospheric system due to increased radiative GHG forcing is less certain. In its 2014 fifth assessment report (AR5), the Intergovernmental Panel on Climate Change (IPCC) reported sea-level rise estimates of up to 0.5m by the end of the century. However, paleoclimate evidence suggests that multi-meter sea level change is possible over a period of a century or more, due to positive feedback mechanisms. This has led to less-conservative predictions of up to several metres of sea level rise this century or shortly thereafter due to ocean thermal expansion, glacier melt and the collapse of land based ice-sheets, namely Greenland and the Western Antarctica.  If indeed positive feedback mechanisms are triggered by current and future increases in AMGST, then this has major implications for low-lying island state nations, such as Singapore.

With each passing month, it is becoming ever more clear that the world needs an ambitious and globally coordinated action to reduce GHG emissions if it is to avoid the ‘dangerous’ climate change referred to by the UNFCC twenty-five years ago.


Hurricanes & Tropical Cyclones: The Link to Climate Change

Posted by Ken on October 22, 2017
Posted under Issue 225

Hurricanes & Tropical Cyclones: The Link to Climate Change

Dr. Jeff Obbard*

*Jeff is a Professor of Environmental Science, currently based at Qatar University. He was previously based at the National University of Singapore, where he served as Director for the Sustainable Development & Water Alliance, and Research Director for the Tropical Marine Science Institute. He has been identified in Singapore as a Top 100 Global Sustainability Leader, and is a recipient of the United Nations Mondialogo Award on sustainable development. Jeff was an invited Expert Reviewer for the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.


September 2017

The devastation of Hurricanes Irma and Maria in the Caribbean in September has prompted questions as to whether the ferocity of these tropical storms was linked to climate change. Whilst impossible to attribute a single weather event to our changing climate, scientific climate observations clearly show that hurricanes and cyclones are set to become more intense and frequent, with concomitant risks for life and property.

Hurricane Irma was both powerful (reaching Category 5) and large (bigger than France), and wreaked havoc across the Caribbean and Florida – killing 82 people in its wake. Irma, the most destructive Atlantic hurricane to strike the United States since Katrina in 2005, reached its peak intensity on 6 September with 185 mph winds. It followed hot on the heels of Hurricane Harvey in August, which dumped record levels of rain on Texas (over 100cm in 4 days) which caused widespread flooding and the displacement of 30,000 people. Irma was shortly followed by Hurricane Maria, initially a Category 5 storm – yet another shot across the bows of the Caribbean. Does this season’s hurricane season have the fingerprints of climate change on it?

The term ‘dangerous anthropogenic climate change’ was first used at the United Nations Framework Convention on Climate Change (UNFCCC) in 1992, when the international community agreed to reduce atmospheric concentrations of greenhouse gases (GHG) with the goal of “preventing dangerous anthropogenic (human) interference with Earth’s climate system”1.  Since then global carbon emissions have increased by almost 50%, and the size of the world’s economy has doubled2. In its latest climate assessment (AR5) the Intergovernmental Panel on Climate Change (IPCC) made clear and  unambiguous statements about the status of climate change i.e.: i) warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia; ii) atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years, and; iii) it is extremely likely (95-100% probability) that human influence was the dominant cause of global warming between 1951-20103.


‘Dangerous climate change has now become synonymous with a ‘policy guiderail’ of limiting the rise in average global mean surface temperatures (AGMST) as a result of human GHG emissions to no more than 2oC above a pre-industrial baseline. This guiderail has become ingrained in climate change policy via a series of UN conferences of the parties (COP) under the UNFCCC framework, culminating in the 2015 Paris Climate Agreement (PCA) which states, as a long-term goal, keeping the increase in AMGST to well below 2°C above pre-industrial levels, with the aim to limit the increase to 1.5°C4.


Although the PCA is commendable, at least from the diplomatic perspective, there is growing concern that the 2oC guiderail is based more on political expediency than scientific accuracy. Certainly, when evaluated in the context of contemporary ‘real-world’ observational changes in the global climate system, and evidence from the Earth’s climate history (or paleoclimate) record, then the 2oC is overly generous and misguided. Analyses of global climate data for the year 2016 by the World Meteorological Organization5, show that AMGST were the highest since instrumental temperature records began in 1880. Temperatures were an average of 1.1oC warmer in 2016 than the mid-20th century mean, with several months in 2016 reaching almost 1.5oC above pre-industrial levels. Indeed, 2016 was the third year in a row to set a new record high for AMGST temperatures, where 16 out of the first 17 years of the 21st century have all exceeded pre-industrial temperature records. More recently, leading climate scientist Dr. James Hansen, has highlighted the risk of extreme summer temperatures as a result of climate change, and concludes that AMGST for 2016 were 1.28oC above average, with the warming trend continuing into 20176.  In short, we are already flirting dangerously with the 1.5oC goal of the PCA.


Hurricanes and tropical cyclones are complex phenomenon: both naturally occurring and notoriously difficult predict – even without the backdrop of rising global temperatures. A changing climate exacerbates the risk of an increased frequency and intensity of storm events, and makes them even more deadly. Higher sea levels, caused by the thermal expansion of the world’s oceans and melting glaciers/ice caps increase storm-surge levels; and higher sea temperatures add fuel to these weather systems which are born over the oceans, and from which they derive their energy. A warmer atmosphere also holds more moisture, where for every extra degree Celsius in warming the atmosphere holds 7% more water (Clausius–Clapeyron equation) which makes rainfall events more extreme. Recently, Hansen et al. (2016)7 highlighted the risk of ‘super-storms’ and accelerated sea level rise if current warming trends, ice-melt and changing atmospheric circulation patterns are allowed to continue. In this context, Hurricanes Harvey, Irma, and Maria are just precursors of the intensity of storms in the future – if climate change is not stopped.

The scientific evidence is clear – in the absence of concerted global GHG emission reductions the risk, frequency and impact of hurricanes and tropical cyclones will increase. Despite the PCA being a landmark achievement in the world’s attempt to avoid dangerous climate change there is still a glaring disparity between the scale of GHG emission reductions actually needed to stay within the 2oC guiderail (let alone 1.5 oC) and those actually pledged under the agreement. Indeed, the International Energy Agency (IEA), has recently stated that current commitments (known as nationally determined contributions, or NDCs) will result a temperature increase of 2.7 oC by 2100, and above 3oC thereafter7. This precarious scenario for future climate security has been further denigrated by the unilateral decision of the United States of America, the world’s second largest GHG emitter after China, to withdraw from the Paris Agreement in June 2017.

On a more positive note, despite the US withdrawal, a renewed international commitment to the goals of Paris Agreement was evident at the COP22 in Morocco in November 2016. Furthermore, COP 23, which will take place in Bonn this November, will place focus on the implementation of the PCA, and aims to galvanize international climate action, despite the US decision.  At a prelude to COP 23, during a September meeting in Montreal of global environment ministers China, Canada and the European Union boldly stated that the goals of the Paris Agreement are irreversible and non-negotiable. The European Union Commissioner for Climate Action and Energy, Miguel Arias Cañete, said that “In the case of collapse of ambitions by the United States, the European Union will make sure to make our planet great again.” This sentiment was echoed by China’s special representative for Climate Change Affairs, Mr. Xie Zhenzua, who said “We cannot let the Paris agreement fail.” For the sake of a cooler and more secure global climate for all, let’s hope massive, coordinated global action prevails.


1. United Nations (9 May 1992), United Nations Framework Convention on Climate Change, New York.

  1. What Lies Beneath. The Understatement of Climate Risks.  Eds. Sprat D. and Dunlop I.

3. IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. R.K. Pachauri and L.A. Meyer (eds.). IPCC, Geneva, Switzerland.

  1. Paris Agreement. United Nations Treaty Collection., 8 July 2016.
  2. World Meteorological Organization (January 2017).   WMO confirms 2016 as hottest year on record, about 1.1°C above pre-industrial era.
  3. Hansen J.  Global temperatures. See:
  4. Hansen J. et al. (2016) Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ◦C global warming could be dangerous.  Atmos. Chem. Phys., 16, 3761–3812.
  5. Energy Technology Perspectives, 2016. International Energy Agency,


Loading the Climate Dice: Wildfires & Global Warming

Posted by Ken on October 22, 2017
Posted under Issue 225

Loading the Climate Dice:  Wildfires & Global Warming

Professor Jeff Obbard

Recent wildfires, notably in California, Spain and Portugal reveal the growing vulnerability of natural ecosystems and human habitation to ongoing climate change. Nothing left but ‘ash and bones’ was the grim description of the aftermath wildfires that swept through Northern California in mid-October that killed at least 38 people and destroyed over 5,000 homes. Later in October, at least another 36 people died as hundreds of fires spread across central and northern areas of Portugal, fanned by strong Atlantic winds from Hurricane Ophelia. This came after an earlier devastating wildfire in Portugal in June which killed 64 people. Across the border in Spain, in Galicia, at least another 3 people died in the most recent wildfires. Although ‘fire season’ is part of life in the post summer semi-arid, warm climates of California, Spain and Portugal, the recent wildfires have been unprecedented.

Fire needs three things to sustain it: fuel, oxygen and heat. Low rainfall causing drought, searing hot temperatures and wind come together to make the perfect recipe for a conflagration. Weather cycles, such as El-Niño events naturally affect levels of precipitation and moisture, and lead to year-by-year variability in the potential for droughts and wildfires. Although no single wildfire can be attributed to climate change, the gradual warming of the planet has now loaded the ‘climate dice’ – where the chance of extreme summer temperatures occurring in any one year is becoming greater. Compared to a 1950-1980 baseline period, the area of the Earth’s land surface now experiencing extreme summer heat has expanded by over 50-times. Such conditions increase the likelihood that, once wildfires are started by lightning strikes or human error, they will be more intense and longer-burning. Indeed, a recent study published in the Proceedings of the National Academy of Sciences indicate that climate change has already played a significant role in making forests in the western U.S. drier and more likely to burn –  nearly doubling the area affected by forest fires over the last three decades. As wildfires become more frequent and intense, the carbon emissions they release will exacerbate the speed of climate change – leading to a feedback loop where more warming leads to more fires, which releases more carbon, which causes more warming, and so on.


This ‘runaway train’ of climate change is of special concern in Southeast Asia where forest fires also release massive amounts of greenhouse gases when the heavy deposits of carbon-rich peat also burn beneath them. As we know in Singapore, the environmental and health costs of wildfires go beyond just the loss of biodiverse ecosystems. Wildfires can rapidly increase local air pollution – exacerbating lung diseases, and causing breathing difficulties – even in healthy individuals.  The costs of wildfires, in terms of risks to human life and health, property damage and forests will only increase unless we tackle climate change.