3 Atmosphere | 2 Climate | 2.2 Pressures affecting Australia's climate
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
At a glance
The energy balance of Earth’s atmosphere is influenced by the presence of trace levels of greenhouse gases (GHGs), such as carbon dioxide, methane, nitrous oxide and water vapour (a major GHG), and natural and industrial aerosols. Since the start of the industrial era (around 1750), human activity (principally the burning of fossil fuels) has caused significant increases in the concentrations of these GHGs. Measurements at global background monitoring stations, such as the Cape Grim Baseline Air Pollution Station in Tasmania, show GHG concentrations continuing to increase in line with long-term trends and future projections. Per person, Australia’s GHG emissions are the largest of any country in the Organisation for Economic Co-operation and Development (OECD) (26.8 tonnes in 2008—nearly twice the OECD average), reflecting Australia’s heavy reliance on fossil fuels for our primary energy.
Under policy settings applicable before the release of the Australian Government’s Securing a Clean Energy Future plan in July 2011, Australia’s emissions were projected to grow by 113 megatonnes of carbon dioxide equivalents (MtCO2-e), or 19.6%, between 2010 and 2020. This would have brought the nation’s annual emissions to 690 MtCO2-e in 2020, an increase of 23% from 2000 levels. The Securing a Clean Energy Future plan aims to achieve Australia’s unconditional emissions reduction target—a reduction of 5% on 2000 levels by 2020. This will require abatement of at least 159 MtCO2-e (23%) in 2020. To achieve Australia’s 15% conditional target, a 31% reduction would be needed.
Since the start of the industrial era (about 1750), the overall effect of human activities on climate has been a warming influence. The human impact on climate during this era greatly exceeds that due to known changes in natural processes, such as solar changes and volcanic eruptions. Intergovernmental Panel on Climate Change26
The energy balance of Earth’s atmosphere is influenced by the presence of trace levels of GHGs, the most important of which are carbon dioxide, methane, short-lived tropospheric ozone, nitrous oxide and the synthetic GHGs (e.g. chlorofluorocarbons [CFCs] and hydrofluorocarbons [HFCs]). Water vapour (a major GHG) and natural and industrial aerosols are also important in the atmospheric energy balance, as is natural variability in solar radiation. However, although the net effect of aerosols is known to be negative, there is considerable uncertainty about its magnitude. Similarly, there is uncertainty about the size of the effect of variations in solar radiation on Earth’s energy balance since the start of the industrial era, although it is known to have been positive.26 The effect of factors such as solar radiation, GHGs and aerosols on the energy balance is termed ‘radiative forcing’ (Box 3.1).
Radiative forcing is defined by the Intergovernmental Panel on Climate Change as ‘ …a measure of the influence a factor [such as greenhouse gases] has in altering the balance of incoming and outgoing energy in the Earth–atmosphere system and is an index of the importance of the factor as a potential climate change mechanism’.
Warming of climate is a response to positive forcings, whereas cooling is a response to negative forcings. ‘Radiative forcing is usually quantified as the rate of energy change per unit area of the globe as measured at the top of the atmosphere and is expressed in units of “watts per square metre”’.
Source: Intergovernmental Panel on Climate Change8
Over the past two and a half centuries, human activity (principally the burning of fossil fuels) has caused significant increases in the concentrations of GHGs (Figure 3.8). In the case of the principal GHG (carbon dioxide), the CSIRO global GHG-observing network recorded a preliminary global atmospheric concentration of 388 ppm (parts per million) for 2010 (Raupach & Fraser,27 updated by CSIRO)—an increase of 39% from 280 ppm, the IPCC’s estimate of pre-industrial levels.28CSIRO observations show that the preliminary global average methane concentration in 2010 was 1796 ppb (parts per billion)—an increase of 157% above estimated pre-industrial levels of 700 ppb. CSIRO observations also show that global nitrous oxide levels in 2010 were 324 ppb, a rise of 20% from pre-industrial levels of 270 ppb.27
ppb = parts per billion; ppm = parts per million
Source: MacFarling Meure et al.29 updated by P Krummell, the Centre for Australian Weather and Climate Research and the Commonwealth Scientific and Industrial Research Organisation, unpublished data
Figure 3.8 Major greenhouse gas levels over the past 1000 years
In addition to the three main GHGs, there is a number of fluorinated gases—such as CFCs, HFCs, perfluorocarbons (PFCs) and sulfur hexafluoride—sourced from a range of industrial processes and from business and home use.27 Although these gases are present in the atmosphere in only trace amounts, they are long lived and have global warming potentials thousands of times that of an equivalent concentration of carbon dioxide when assessed on a 100-year timescale.30 They can therefore contribute significantly to global warming in the medium to long term and are included in the set of gases (HFCs, PFCs, sulfur hexafluoride) covered by Annex A of the Kyoto Protocol (an international agreement aimed at stabilising GHG concentrations in the atmosphere). The production and consumption of CFCs and other ozone depleting substances (ODSs) are covered by the Montreal Protocol on Substances that Deplete the Ozone Layer (see Sections 3.2.1 and 3.3.1).
Fluorinated gases made up around 12% of total global radiative forcing due to GHGs in 2010, similar to the situation in 1995 (13%). Under scenario A1B of the IPCC Special report on emissions scenarios, their contribution to global radiative forcing will decrease to 6% by 2100 (Raupach & Fraser,27 updated by CSIRO), reflecting the gradual decline in CFCs in the atmosphere and increasing levels of HFCs.
The increased concentrations of human-generated GHGs have resulted in an increased absorption in the lower atmosphere of the heat radiated from Earth’s surface, causing a rise in the global mean surface temperature of 0.74 ± 0.18 °C over the century from 1906 to 2005.31 However, this rise did not occur uniformly across the century, as average global temperatures did not increase between the 1940s and the 1970s.32 More recently, the 1998–2008 decade was characterised by little warming overall and a decrease of 0.2 °C between 2005 and 2008 (followed by an increase in 2009 and 2010, the most recent years for which data are available).33
Based on their analysis of this recent hiatus in warming, Kaufman et al.33 concluded that the warming effects of GHG emissions during 1998–2008 have been partially offset by a combination of natural and anthropogenic (human-generated) factors. The natural factors (which were largely responsible for the offset) were a decline in solar insolation (a measure of the solar radiation energy received by Earth in a given time) as part of a normal 11-year cycle, and a cyclical shift from El Niño to La Niña conditions. These were supplemented by the anthropogenic factor—a rapid rise in short-lived emissions of sulfur due to large increases in coal use across Asia, particularly China. The sulfate aerosols formed by these emissions absorb solar radiation and reflect sunlight back into space (resulting in a negative radiative forcing). Sulfate aerosols, together with other pollutants, are thought to be largely responsible for the lack of increase in average global temperature over the 1940s to 1970s.34
Although Kaufman et al33 concluded that the recent hiatus in warming resulted principally from natural factors, they stressed that this does not contradict the IPCC’s statement that ‘most of the global average warming over the past 50 years is very likely due to anthropogenic GHG increases …’.8
Each of the six greenhouse gases listed under Annex A of the Kyoto Protocol has a different greenhouse warming potential. The term ‘carbon dioxide equivalent’ (CO2-e) refers to a single measure that combines the global warming effect of all the Annex A gases into a single meaningful number. Specifically, CO2-e is the emissions of carbon dioxide that would cause the same heating of the atmosphere as a particular mass of Annex A greenhouse gases. The Annex A greenhouse gases are carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride.35–36
Measurements at global background monitoring stations, such as the Cape Grim Baseline Air Pollution Station in Tasmania, show carbon dioxide and nitrous oxide concentrations continuing to increase, in line with long-term trends and future projections, whereas methane levels, after a decade-long pause, have resumed rising since 2007. The reasons for this variability in the growth rate of methane concentrations are complex, but the period of stability in the late 1990s and early years of this century was probably due to a reduction in the rate of growth of emissions from the oil and gas industry and an approach to equilibrium, where anthropogenic methane releases are matched by the atmosphere’s ability to remove methane. Growth in emissions since 2007, which has occurred in the Arctic and in the tropics, may be caused by increased releases from wetlands due to unusually high temperatures (Arctic) and precipitation (tropics).37
In absolute terms, Australia’s emissions of GHGs (558 megatonnes of megatonnes of carbon dioxide equivalents [MtCO2-e]) appear small alongside major emitters such as China and the United States (7233 MtCO2-e and 6914 MtCO2-e, respectively), but they are not insignificant, being on a par with countries such as France, Italy and the Republic of Korea (550–570 MtCO2-e per year; all data are for 2005).38 Per person, Australia’s emissions are the largest of any Organisation for Economic Co-operation and Development (OECD) country—26.8 tonnes in 2008, nearly twice the OECD average (Figure 3.9).12-13
CO2-e = carbon dioxide equivalents; OECD = Organisation for Economic Co-operation and Development
Sources: Garnaut13 and DCC 2008, National Greenhouse Gas Inventory 2006; International Energy Agency
Figure 3.9 Greenhouse gas emissions per person
The energy sector (comprising stationary energy, transport and fugitive emissions from fuels) continues to be the dominant source of Australia’s GHG emissions, accounting for 74% of net emissions, including those associated with land use, land-use change and forestry (LULUCF) (Figure 3.10). Within this sector, stationary energy accounts for 52%, comprising electricity (37%) and fuel combustion (15%).
LULUCF = land use, land-use change and forestry
Source: Australian Government Department of Climate Change and Energy Efficiency39
Figure 3.10 Greenhouse emissions by sector, Kyoto accounting, 2009
Australia’s very high level of emissions per person reflects the nation’s heavy reliance on fossil fuels as a primary energy source and, in particular, the dominant role of coal (an emissions-intensive fuel) in the production of electricity (Figure 3.11).
Fuel mix contributing to total primary energy supply, 2008
Source: International Energy Agency40
Figure 3.11 Fuel mix contributing to total primary energy supply, 2008
Although the transport and agricultural sectors both contribute around a sixth of Australia’s net GHG emissions, transport’s contribution is almost entirely through emissions of carbon dioxide, whereas agriculture’s contribution is through methane and nitrous oxide—gases with global warming potentials many times that of carbon dioxide (Figure 3.12). (The 100-year warming potential of methane is 21 times that of carbon dioxide; the figure for nitrous oxide is 310.)41
Under Article 3.3 of the Kyoto Protocol, parties can use net changes in GHG emissions associated with direct human-induced LULUCF activities that occurred since 1990 to meet their emission reduction commitments. Australia, in meeting its obligations to account for its GHG emissions under the protocol, includes net emissions associated with LULUCF. However, these tend to vary significantly from year to year, reflecting variability in climate; peaks (such as in 2007) are associated with extreme events such as bushfires and drought, which lead to major loss of carbon from vegetative and soil sinks.
LULUCF = land use, land-use change and forestry
Source: Australian Government Department of Climate Change and Energy Efficiency39
Figure 3.12 Carbon dioxide, methane and nitrous oxide emissions by sector, Kyoto accounting, 2009
As a signatory to the Kyoto Protocol (ratified in 2007), Australia is committed to limiting increases in net GHG emissions to 108% of its 1990 levels by 2008–2012 (the ‘Kyoto commitment period’). As reported in 2010 in its Fifth national communication on climate change (under the United Nations Framework Convention on Climate Change),42 Australia remains on track to meet this commitment, largely due to a major reduction in emissions associated with LULUCF (80% from 1990 to 2008) and, more particularly, to less land clearing over the same period (Figure 3.13).42
CO2-e = carbon dioxide equivalents
Source: Adapted from Australian Government Department of Climate Change and Energy Efficiency42 with permission
Figure 3.13 Australian greenhouse gas emissions, 1990–2012 (projected), including emissions associated with land use, land-use change and forestry
In contrast, from 1990 to 2009, emissions (excluding LULUCF) grew by 30.5% (Figure 3.14). The largest increase was in the stationary energy sector, which includes emissions from fuel consumption for electricity generation; fuels consumed in the manufacturing, construction and commercial sectors; and other sources such as domestic heating. This sector grew by 51%, driven by a mix of factors, notably rising population and household incomes, and growth in demand for energy associated with substantial increases in the export of resources. In the same period, transport grew by 35% in response to increases in the number of vehicles. Fugitive emissions (which typically result from leaks during the production, processing, transport, storage and distribution of raw fossil fuels) increased by 23%, chiefly because of increased emissions from coal mines. Emissions due to industrial processes rose by 21%, principally associated with increased production of HFCs as substitutes for ozone depleting CFCs, and substantial (220%) growth in emissions from the chemical industry.39,42–43
The waste and agricultural sectors are the only ones to have recorded a decline in emissions from 1990 to 2009 (22% and 2%, respectively). In the waste sector, this reflected the increasing capture of methane from landfill in response to a combination of regulatory pressure and commercial gain (through use of the emissions as a source of energy). In agriculture, increases in emissions during the 1990s due to rising fertiliser use and savanna burning have been reversed since 2002, reflecting reduced fertiliser use and a significant drop in crop and animal production due to drought.39,42–43
CO2-e = carbon dioxide equivalents. Note: Figures for 2009–10 are preliminary estimates.
Source: Australian Government Department of Climate Change and Energy Efficiency,39 with permission
Figure 3.14 Net greenhouse gas emissions by sector, excluding land use, land-use change and forestry
Since 2000, Australia’s emissions of GHGs (excluding LULUCF) have grown by an average of 1.1% per year. This compares with average annual growth of 1.9% from 1990 to 2000. The difference is principally attributable to a slower rate of growth of emissions from stationary sources and transport, as well as a decrease in emissions from agriculture. Like most OECD countries, Australia experienced a reduction in annual GHG emissions during the global financial crisis. However, the reduction was only marginal, with emissions (excluding LULUCF) falling from 551 MtCO2-e in 2008 to 546 MtCO2-e in 2009—a fall of 0.9%.39 By comparison, the United States and the European Union experienced reductions in emissions growth of approximately 7% during the same timeframe.44
This marginal decline in Australia’s emissions is only a minor and temporary divergence from the continuing longer term growth trend (Figure 3.15).
CO2-e = carbon dioxide equivalents; Mt = megatonne
Source: Australian Government Department of Climate Change and Energy Efficiency45
Figure 3.15 National Greenhouse Gas Inventory, actual quarterly emissions estimate and trend emission estimate, June quarter 2000 – June quarter 2010
The national inventory does not include estimates of net emissions from Article 3.3 of the Kyoto Protocol (land use, landuse change and forestry activities), which are estimated on an annual basis only. Emission estimates have been compiled by the Australian Government Department of Climate Change and Energy Efficiency using the methods incorporated in the Australian Greenhouse Emissions Information System, preliminary activity data obtained under the National Greenhouse and Energy Reporting System and from a range of publicly available sources—principally the Australian Bureau of Agricultural and Resource Economics and Sciences, the Australian Bureau of Statistics, the Australian Energy Market Operator and the Australian Government Department of Resources, Energy and Tourism. As more data become available from these sources—in particular the National Greenhouse and Energy Reporting System—these preliminary activity data will be replaced and the estimates of emissions revised before submission to the United Nations. The department’s assessment is that the 90% confidence interval for the national inventory (before taking account of Article 3.3 activities) is ± 1% (i.e. there is a 90% probability that future revisions will be limited to ± 1% of the current estimate).
Under policy settings applying before the release of the Australian Government’s Securing a Clean Energy Future plan, Australia’s emissions were projected to grow by some 113 MtCO2-e (19.6%) from 2010 to 2020. This would have brought Australia’s annual emissions (including LULUCF) to 690 MtCO2-e in 2020, an increase of 23% from 2000 levels. The projected growth was mainly due to anticipated emissions from the extraction and processing of energy resources to meet expected continued strong export demand. This contrasted with previous decades, when most emissions growth related to electricity generation. From 2010 to 2020, emissions from electricity generation were projected to grow much more slowly than in the past, increasing by only 6% (12 MtCO2-e). This reflected the factoring into the projection of a significant increase in the use of renewable energy sources for generation of electricity, in response to the Renewable Energy Target. The target, which was established by the Australian Government in 2009, aims to ensure that 20% of Australia’s electricity supply comes from renewable sources by 2020.46 The Securing a Clean Energy Future plan aims to achieve Australia’s unconditional emissions reduction target—a reduction of 5% on 2000 levels by 2020. This will require abatement of at least 159 MtCO2-e (23%) in 2020.47(See Section 2.3.2 for details of the plan.)
CSIRO and the Bureau of Meteorology’s latest State of the climate report48 concludes that, in the coming decades, Australia will be hotter and much of the continent will be drier. More specifically, the report summarises the main direct effects of climate change as follows:
- By 2030, projections show average temperatures rising by 0.6–1.5 °C, in addition to an existing rise of around 0.7 °C since 1960.
- By 2070, if growth in GHG emissions continues in line with past trends, projected warming will be in the range of 2.2–5.0 °C. Even at the lower end of this range, the projected increase is near or above the level regarded by many climate scientists as likely to trigger ‘dangerous climate change’. (See Schneider and Lane49 for a discussion of the complexities of the concept of dangerous climate change.)
- Compared with the last two decades of the 20th century, southern Australia is likely to experience reduced winter rain, and spring rainfall declines are expected in southern and eastern areas. In south-west Western Australia, reductions in autumn rainfall are likely to add to pressures associated with the existing decades-long decline in winter rain. Northern Australia is likely to experience an increase in annual and summer rainfall.50
In addition to directly affecting large-scale aspects of climate, such as average temperature and precipitation, human-induced climate change has the potential to alter the frequency and severity of extreme events, such as storms, floods, droughts and heatwaves.50–53 As noted above, separating the effect of climate change from that of natural processes can be difficult, and this uncertainty greatly complicates efforts to characterise likely changes in these extreme events. Nevertheless, improving our understanding of the vulnerabilities associated with such changes is an essential step in planning our adaptation to climate change.54
Direct effects on climate, such as those outlined in Section 2.2.3, trigger indirect effects further down a complex chain of cause and effect. These are products of the profound and pervasive influence of climate, both on a host of natural processes that underpin the condition and trend of ecosystems, and on a range of demographic, economic and social processes and systems. The complex nature of the effects of changes in climate is illustrated in Figure 3.16 in relation to human health.
Source: Redrawn from McMichael et al.,55 with permission
Figure 3.16 Pathways by which climate change affects human health, including local modulating influences and the feedback influence of adaptation measures
Australia’s Fifth national communication on climate change (under the United Nations Framework Convention on Climate Change)42 draws on the work of the IPCC25 to outline a wide range of indirect effects of climate change:
- decreased water availability and water security, due to
- reduced rainfall in southern Australia and south-west Western Australia
- increased evaporation, which reduces run-off to streams and recharge of groundwater systems
- coastal zone impacts, such as inundation from sea level rise
- damage to energy, water, communications and built infrastructure
- a decline in agricultural productivity due to increased drought and fire
- damage to iconic natural ecosystems, such as the Great Barrier Reef and Kakadu National Park
- a decline in biodiversity.
Other sources identify additional indirect effects of climate change, such as:
- likely increases in the frequency of days of extreme bushfire risk,56–58 and of dust storms, linked to widespread reductions in levels of soil moisture25
- changes to human health, including
- some positive, particularly in the first part of the century, when some areas will benefit from a reduction in cold weather
- some negative, resulting from factors such as more frequent and intense heatwaves, particularly later in the century (Table 3.1), and possible extension in the range of various disease vectors (notably mosquitoes).13,25,59
|In the baseline case, any increase in number of deaths is due to the expanding and ageing of the population. The next three cases are best-estimate cases and use the 50th percentile rainfall and relative humidity and 50th percentile temperature for Australia. The final case (right-hand side) is an illustrative ‘bad-end story’ that uses the 10th percentile rainfall and relative humidity and 90th percentile temperature for Australia (a hot, dry extreme).|
|Baseline—no human-induced climate change||No-mitigation case||Global mitigation with CO2-e stabilisation at 550 ppm by 2100||Global mitigation with CO2-e stabilisation at 450 ppm by 2100||Hot, dry extreme case|
|Number of temperature-related deaths in 2030 and 2100|
|NSW||2 552||2 754||2 316||1 906||2 290||2 224||2 268||2 334||2 255||2 040|
|Qld||1 399||1 747||1 276||5 878||1 274||1 825||1 278||1 664||1 286||11 322|
|Vic||1 788||1 966||1 632||1 164||1 614||1 586||1 599||1 673||1 589||1 021|
|Australia||7 717||8 562||7 115||11 234||7 061||7 590||7 020||7 638||6 999||17 199|
ACT = Australian Capital Territory; CO2-e = carbon dioxide equivalent; NSW = New South Wales; NT = Northern Territory; ppm = parts per million; Qld = Queensland; SA = South Australia; Tas = Tasmania; Vic = Victoria; WA = Western Australia
During the second half of January 2009, Victoria experienced an unprecedented heatwave. Maximum day-time and night-time temperature records were broken by significant margins, and new records were set for the duration of extreme heat. From 27 to 31 January, much of Victoria experienced maximum temperatures 12–15 °C above normal. For three of these days (28–30 January), the maximum was above 43 °C, peaking at 45.1 °C on January 30.
|Maximum day-time temperature (°C)||Maximum night-time temperature (°C)||Mean temperature (°C)|
|Monday 26 January||25.5||14.4||19.9|
|Tuesday 27 January||36.4||16.6||26.5|
|Wednesday 28 January||43.4||18.8||31.1|
|Thursday 29 January||44.3||25.7||35.0|
|Friday 30 January||45.1||25.7||35.4|
|Saturday 31 January||30.5||22.5||26.5|
|Sunday 1 February||33.8||20.3||27.0|
The impact of the heatwave on public health was clearly identifiable and substantial. The effects were similar to those of the catastrophic 2003 European heatwave, which had an estimated total excess mortality of 70 000. In Victoria, the Department of Health calculated a figure of 374 excess deaths over the average number in the same weeks of the preceding five years (an increase of 62% in all-cause mortality).
In addition to this marked spike in mortality, there was a pronounced impact on morbidity, which was reflected in increases in ambulance emergency case load (46% over the three hottest days), locum general practitioner visits (almost four-fold increase in heat-related attendances), and emergency room attendances (eight-fold increase in heat-related presentations). Not surprisingly, as shown in Figure A, the elderly were the group most affected, with people over 75 years of age being disproportionately represented in both mortality and morbidity.
As with any extreme climatic event, estimating the extent to which climate change played a role over and above natural variability is problematic. Nevertheless, an increase in the frequency of such extreme temperature-driven events is entirely consistent with the now decades-long upward trend of average temperatures and with the results from studies modelling a broad range of climate change scenarios.
These data from the Registrar and the State Coroner’s Office are provisional and, although these are expected to account for the vast majority of deaths, may be revised over time. It is possible that deaths relating to the heatwave occurred or were reported outside the period of analysis, thereby underestimating the impact. Certainly, the vast majority of short-term mortality is expected to have been captured.
Source: Department of Human Services Victoria,60 using data from the Bureau of Meteorology and the Victorian Registry of Births, Deaths and Marriage
Figure A Deaths in Victoria by age group between 26 January and 1 February, 2004–08 and 2009
|Very high impact||High impact||Low impact||Very low impact||in grade||in trend|
|Greenhouse gases||Under policy settings applying before the release of the Australian Government’s Securing a Clean Energy Future plan, Australia’s emissions were projected to grow by 113 MtCO2-e (19.6%) between 2010 and 2020. This would have brought Australia’s annual emissions (including emissions from land use, land use change and forestry) to 690 MtCO2-e in 2020, an increase of 23% from 2000 levels. To achieve the nation’s minimum target of a 5% cut on 2000 levels by 2020 will require a reduction of 159 MtCO2-e (23% compared with the projected 2020 level). The Securing a Clean Energy Future plan aims to achieve this reduction by 2020. To achieve Australia’s 15% conditional target, a 31% reduction would be needed
Climate change modelling indicates that average temperatures will rise, the number of dry days will increase, and intense rainfall events will increase in many areas. More frequent bushfires, dust storms and heatwaves and attendant impacts on human health can all be expected
|Recent trends||Improving||Stable||Confidence||Adequate high-quality evidence and high level of consensus|
|Deteriorating||Unclear||Limited evidence or limited consensus|
|Evidence and consensus too low to make an assessment|
|Very low impact: Few or no impacts have been observed, and accepted predictions indicate that future effects are likely to be minor|
|Low impact: Current pressures have been observed to have had a limited impact on some aspects of climate, and there is concern that, based on accepted predictions, these may worsen|
|High impact: Current pressures are probably already having serious impacts on important aspects of climate and are expected to worsen, with serious implications for a broad range of areas|
|Very high impact: Current pressures are already having very serious impacts on important aspects of climate (such as temperature, rainfall and extreme events) with very serious flow-on effects in a broad range of areas|
MtCO2-e = megatonnes of carbon dioxide equivalent