Earlier this week, the media carried a series of articles suggesting that the threshold of limiting increased global temperature to 1.50 C had already been crossed. The articles are based on new research on ocean temperatures that surmised that "hotter land temperatures, together with the earlier onset of industrial-era warming, indicate that global warming was already 1.7 +/- 0.1C above pre-industrial levels by 2020". In short, this research and possible discovery means that the temperature is 0.5C higher than IPCC estimates with 20 C projected by the late 2020s, nearly two decades earlier than expected.
A team led by Professor Malcolm McCulloch from the University of Western Australia studied 300 years of records preserved in the skeletons of long-lived sea sponges from the Eastern Carribean. Of particular importance the sclerosponge thermometry shows that global warming has already exceeded 1.50 C. The focus of the research was changes in the amount of a chemical known as 'strontium' in the sponges skeletons. The changes in the amount of strontium reflects variations in seawater temperatures over the sponges' life.
The conclusion reached is that the Earth may already have reached at least 1.7C warming since pre-industrial times, well above the Paris Climate target of 1.5C. The opportunity for controlling climate change at the first milestone has already been lost.
Climate scientists don’t like surprises. It means our deep understanding of how the climate works isn’t quite as complete as we need. But unfortunately, as climate change worsens, surprises and unprecedented events keep happening.
In March 2022, Antarctica experienced an extraordinary heatwave. Large swathes of East Antarctica experienced temperatures up to 40°C (72°F) above normal, shattering temperature records. It was the most intense heatwave ever recorded anywhere in the world.
So shocking and rare was the event, it blew the minds of the Antarctic climate science community. A major global research project was launched to unravel the reasons behind it and the damage it caused. A team of 54 researchers, including me, delved into the intricacies of the phenomenon. The team was led by Swiss climatologist Jonathan Wille, and involved experts from 14 countries. The collaboration resulted in two groundbreaking papers published today.
The results are alarming. But they provide scientists a deeper understanding of the links between the tropics and Antarctica – and give the global community a chance to prepare for what a warmer world may bring.
Head-hurting complexity
The papers tell a complex story that began half a world away from Antarctica. Under La Niña conditions, tropical heat near Indonesia poured into the skies above the Indian Ocean. At the same time, repeated weather troughs pulsing eastwards were generating from southern Africa. These factors combined into a late, Indian Ocean tropical cyclone season.
Between late February and late March 2022, 12 tropical storms had brewed. Five storms revved up to become tropical cyclones, and heat and moisture from some of these cyclones mashed together. A meandering jet stream picked up this air and swiftly transported it vast distances across the planet to Antarctica.
Below Australia, this jet stream also contributed to blocking the eastward passage of a high pressure system. When the tropical air collided with this so-called “blocking high”, it caused the most intense atmospheric river ever observed over East Antarctica. This propelled the tropical heat and moisture southward into the heart of the Antarctic continent.
Luck was on Antarctica’s side
The event caused the vulnerable Conger Ice Shelf to finally collapse. But the impacts were otherwise not as bad as they could have been. That’s because the heatwave struck in March, the month when Antarctica transitions to its dark, extremely cold winter. If a future heatwave arrives in summer – which is more likely under climate change – the results could be catastrophic.
Despite the heatwave, most inland temperatures stayed below zero. The spike included a new all-time temperature high of -9.4°C (15.1°F) on March 18 near Antarctica’s Concordia Research Station. To understand the immensity of this, consider that the previous March maximum temperature at this location was -27.6°C (-17.68°F). At the heatwave’s peak, 3.3 million square kilometres in East Antarctica – an area about the size of India – was affected by the heatwave.
The impacts included widespread rain and surface melt along coastal areas. But inland, the tropical moisture fell as snow – lots and lots of snow. Interestingly, the weight of the snow offset ice loss in Antarctica for the year. This delivered a temporary reprieve from Antarctica’s contribution to global sea-level rise.
These images, acquired by the Copernicus Sentinel-2 satellites on January 30 2022 (left) and March 21 2022 (right), show the Conger ice shelf before and after the collapse, which was triggered by a shocking heatwave.European Union, Copernicus Sentinel-2 satellite imagery, CC BY
Learning from the results
So what are the lessons here? Let’s begin with the nice bit. The study was made possible by international collaboration across Antarctica’s scientific community, including the open sharing of datasets. This collaboration is a touchstone of the Antarctic Treaty. It serves as a testament to the significance of peaceful international cooperation and should be celebrated.
Less heartwarmingly, the extraordinary heatwave shows how compounding weather events in the tropics can affect the vast Antarctic ice sheet. The heatwave further reduced the extent of sea ice, which was already at record lows. This loss of sea ice was exacerbated this year resulting in the lowest summer and winter sea ice ever recorded. It shows how disturbances in one year can compound in later years.
The event also demonstrated how tropical heat can trigger the collapse of unstable ice shelves. Floating ice shelves don’t contribute to global sea-level rise, but they acts as dams to the ice sheets behind them, which do contribute.
This research calculated that such temperature anomalies occur in Antarctica about once a century, but concluded that under climate change, they will occur more frequently.
The findings enable the global community to improve its planning for various scenarios. For example, if a heatwave of similar magnitude hit in summer, how much ice melt would there be? If an atmospheric river hit the Doomsday glacier in the West Antarctic, what rate of sea level rise would that trigger? And how can governments across the world prepare coastal communities for sea level rise greater than currently calculated?
This research contributes another piece to the complex jigsaw puzzle of climate change. And reminds us all, that delays to action on climate change will raise the price we pay.
This article has been amended to correct an error in converting a 40°C temperature difference from Celsius to Fahrenheit.
The latest State of the Climate Report for 2022 has been published by the CSIRO and the Bureau of Meteorology (BOM) continuing the unequivocal evidence of climate change and the impact on weather that is becoming the normal for this continent. The findings in summary provide sober reading at best and a portent of what is to come in the years ahead -
Temperature: Australia’s climate has warmed by an average of 1.47 ± 0.24 °C
since national records began in 1910.
Sea temperature: Sea surface temperatures have increased by an average of 1.05 °C
since 1900. This has led to an increase in the frequency of extreme heat events
over land and sea.
Rainfall: There has been a decline of around 15 per cent in April to October
rainfall in the southwest of Australia since 1970. Across the same region, May
to July rainfall has seen the largest decrease, by around 19 per cent
since 1970.
There has been a decrease in streamflow at most gauges across Australia
since 1975.
Rainfall and streamflow have increased across parts of northern
Australia since the 1970s.
Fire: There has been an increase in extreme fire weather, and a longer fire
season, across large parts of the country since the 1950s.
There has been a decrease in the number of tropical cyclones observed in
the Australian region.
Decrease in snow: Snow depth, snow cover and number of snow days have decreased in alpine
regions since the late 1950s.
Ocean acidification: Oceans around Australia are acidifying and have warmed by more than
1 °C since 1900, contributing to longer and more frequent
marine heatwaves.
Sea level rise: Sea levels are rising around Australia, including more frequent extremes
that are increasing the risk of inundation and damage to coastal infrastructure
and communities.
Aerial survey (c) Great Barrier Marine Park Authority
The lastest surveillance report on Australia's Great Barrier Reef confirms the ongoing damage to the reef through increased temperatures as a result of climate change. Of particular alarm has been the repeated events of bleaching which now number 4 in seven years. The expected relief from a change in weather systems to La Nina did not occur and a mass bleaching resulted. This prolonged heat exposure is occuring across the wider reef system.
The latest reef snapshot report published this month (May 2022) describes the current situation in clear terms which are not easily disputed -
A total of 719 reefs were surveyed from the air between the Torres Strait and the Capricorn Bunker Group in the Great Barrier Reef Marine Park. Of these 654 reefs (91 per cent) exhibited some fomr of bleaching and a significant core of the central reef had severe or extreme bleaching.
Coral bleaching seen from the air is largely consistent with the spatial distribution of heat stress accumulation with a larger proportion of coral cover bleached on reefs that were exposed to the highest accumulated heat stress this last Summer (late 2021 and early 2022)
The waters around the Great Barrier Reef exceeded historical summer maximums for the hottest summer months with three distinct heat waves increasing thermal stress throughout the Central and Northern Great Barrier Reef.
The 2022 Aerial Survey Map [shown above] illustrates the variation in bleaching observed across the reef in the second half of March. The aerial surveys were conducted by trained observers from the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science.
As part of the Sixth Assessment Report, working group II of the IPCC published the 'report on impacts, adaptation and vulnerability'. This specific paper contains a list of impact indicators in a graphical presentation covering both ecological and human impact measures (as shown below). Copyright IPCC 2022.
The latest report from Intergovernmental panel on climate change (IPCC) continues the well established trend of identifying the sadly lagging response to the threat of climate change globally. While a few concrete steps have been taken to address carbon emissions and mitigation, these efforts remain substantially insufficient and in many cases, badly misdirected.
A number of messages in the report emphasise the importance of close collaboration between all parts of society: Government, private sector, media, the scientific community, investors and essentially international cooperation.
There is also a sense that many of the 'soft limits' to human adaptation have been reached and increasingly the next steps will be harder to achieve with options now increasingly closing off with the risk of cascade events more likely.
Key points covered in this report -
it is unequivocal that climate change has already disrupted human and natural systems. Past and current development trends (past emissions, development and climate change) have not advanced global climate resilient development.
climate resilient development prospects are increasingly limited if current greenhouse gas emissions do not rapidly decline, especially if 1.5C global warming is exceeded in the near term. the Report also noted that " evidence of observed impacts, projects risks, levels and trends in vulnerability, and adaptation limits, demonstrate that worldwide climate resilient development action is more urgent than previously assessed in the 5th Assessment Report".
the rise in weather and climate extremes has led to some irreversible impacts as natural and humans systems are pushed beyond their ability to adapt.
approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change.
climate change impacts and risks are becoming increasingly complex and more difficult to manage. Multiple climate hazards will occur simultaneously and multiple climatic and non climatic risks will interact resulting in compounding overall risk and risks cascading across sectors and regions.
Note a key caveat about global warming that transiently exceeds 1.5C which is termed 'overshoot'. "Depending on the magnitude and duration of overshoot, some impacts will cause the release of additional greenhouse gases and some will be irreversible even if global warming is reduced".
Most people would be aware that the Earth's rotational axis is not steady but tends to wobble as the planet is not a perfect unchanging sphere. Due to plate tectonics, erosion, weather masses moving around the surface, large ice masses weighting down sections of land, the poles actually move and this drift averages around 6 centimetres a year. This movement for example drew the North Pole towards Labrador in a Southerly direction. For compass users, this situation will be familiar due to the adjustment calculation needed for grid to magnetic measurement to compensate for the drift when navigating using maps.
However in 2005 this drift suddenly altered and shifted to an Easterly direction and accelerated corresponding to an increase in the melt occuring in Greenland and Antarctica. Researchers at the University of Texas in Austin found using the GRACE (Gravity Recovery and Climate Experiment) satellites that around 600 gigatonnes of mass was being lost each year by the large glaciers in Greenland, Antarctica and the mountain glaciers. This mount of water being released from the glaciers into the oceans accounted for 90 % of the polar drift since 2005. In short the planet's tilt was unexpectedly altered due to the effect of climate change.
The 6th Assessment Report from the IPCC makes for sobering reading and was issued prior to COP26 in Glasgow. In summary, the report has found that:
Human induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones has strengthened since the 5th Assessment Report.
Global surface temperatures will continue to increase until at least mid-century under all emission scenarios considered. Global warming of 1.5C and 2C will be exceeded during the 21st century unless deep reduction in carbon dioxide (CO2) and other greenhouse gas emissions occur in the coming decades.
Under scenarios with increasing CO2 emissions, the ocean and land carbon sinks are projected to be less effective at slowing the accumulation of CO2 in the atmosphere.
Continued global warming is projected to further intensify the global water cycle including its variability, global monsoon precipitation and the severity of wet and dry events.
With further global warming, every region is projected to increasingly experience concurrent and multiple changes in climatic impact-drivers.
Low-likelihood outcomes such as ice sheet collapse, abrupt ocean circulation changes, some compound extreme events and warming substantially larger than the assessed 'very likely' range cannot be ruled out.
Strong rapid and sustained reduction in CH4 (methane) would also limit the warming effect resulting from declining aerosol pollution and would improve air quality.
The report now finds that serious climate impacts that previously were thought to be less likely, are now considered to be possible due to the accelerated increase in global warming.
In March this year, the Australian Academy of Science issued a stark warning on the future of this country if global warming is not actively slowed and ultimately stopped. The Academy's report charts both proven existing impacts and the effects of modelled temperature increases. The situation could not be more starkly or clearly demonstrated by the findings of the Academy which included -
Temperature rising
the total emission reduction current pledged by the Australian and international government through the United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement, even if implemented on time will translate as an average global surface temperatures of 3 degrees Celsius (C) or more.
the planet is well on its way to devastating climate change with average surface temperatures being at 1.1 degrees C above the pre-industrial period. Australia has had a worse outcome with warming on average by 1.4 degrees C.
limiting climate change to 1.5 degrees Celsius in now virtually impossible.
Ecosystems
land-based environments have been affected by drought, fire, extreme heatwaves, invasive species and disease, large scale mortality of trees, birds and tree-dwelling mammals
rising sea levels are amplifying storm impacts damaging coastal ecosystems such as coral reefs and mangrove forests.
Australian agriculture, forestry, fisheries and food security
reduced water availability and heat stress have contributed to reductions in profitability for broadacre crops such as wheat and barley in the magnitude of up to 22% since 2000.
heat stress is a significant issue for livestock systems due to impacts on animal welfare, reproduction and production. Projected temperature and humidity changes suggest an increased number of heat stress days per year.
forestry is facing growing pressure from a warming and drying climate with increased fire risks, changes in rainfall patterns and species-specific pest impacts.
Australian cities and towns
with close to 90% of Australians living in cities and towns, climate change experience will be manifested in various ways.
extreme heat wave conditions, bushfires and storms already place pressure on power stations and infrastructure while simultaneously increasing demand for energy supply for air conditioning.
global sea level rises are already occuring and pose a severe risk to properties infrastructure and ecosystems with coastal flooding becoming a more regular feature. 160,000 to 250,000 coastal properties will be at risk with a rise of 1 metre in sea levels.
climate sensitive infectious diseases such as Ross River fever and other vector borne diseases shift their geographical distribution and intensity of transmission. This will only increase as climate change increases to above 2 degrees C.
The Academy's report provides sober reading and a reality check for those who believe that its only a question of avoiding a 1.5C temperature impact to avoid climate change. The climate crisis has already commenced - the only viable objective is to prevent it becoming worse.
In late 2019, one of Australia's major commercial insurance companies, IAG, in collaboration with the National Centre for Atmospheric Research in the United States, released a report outlining the increased severe weather which will occur as a result of climate change. The report models impacts at 1.5C, 2C and +/- 2 degrees Celsius and makes for better understanding of the direct weather events caused by climate change rather than the larger global impacts of melting polar ice, acidification of oceans, higher temperatures and mega storms.
The report should probably have garnered greater interest at the time of release given it was commissioned by a large commercial insurer. The overall tenor of climate debate in Australia and political dynamic would not have been conducive to ensuring it received sufficient attention.
Of note, IAG's perspective is "... the level of knowledge has now reached the stage where it is possible to make confident assessment of the impacts of climate change at larger scales and longer time frames with objective assessment of the associated levels of confidence.." This, of course, contradicts those political naysayers who believe the evidence of climate change is still contestable.
The report provides key six assessments which are summarised briefly below and given events of the past few months, many of these assessments have been shown to be accurate -
While the frequency of named tropical cyclones in the Australian region, the proportion of the most destructive tropical cyclones has increased at the expense of the more weaker systems. Tropical cyclone risks are therefore expected to increase rapidly in south-east Queensland, north-east NSW regional followed by coastal districts in Western Australia.
Intense short duration rainfall is expected to increase almost everywhere in Australia , resulting in more frequent flooding in urban areas and in small river catchments.
Areas of large hail (2.0-4.9cm in diameter) and giant hail (>5.0cm in diameter) should progressively move southwards with a large increase in the risk to the regions inland from the Hunter River, southwards through the central and southern highlands of New South Wales and central to eastern Victoria.
The multi-day impacts of east coast lows on the south-eastern seaboard of Australia are expected to increase due to wind-driven rainfall ingress, flash and riverine flooding.
Bushfire risk, as measured by the trends in fire danger indices is likely to increase in all locations nationally leading to more frequent and extreme events and longer fire seasons.
Sea level rise is expected to accelerate around the Australian coastline but at differing rates. It is notable that past assessments of sea level rise are lower than those that recent observations show.
In light of actual recent new data, the IAG report may yet prove to still under-estimate the full weather impact which will be felt sooner rather than later.
