Climate change - entering a new phase ?

Earth is already shooting through the 1.5°C global warming limit, two major studies show

Andrew King, The University of Melbourne and Liam Cassidy, The University of Melbourne

Earth is crossing the threshold of 1.5°C of global warming, according to two major global studies which together suggest the planet’s climate has likely entered a frightening new phase.

Under the landmark 2015 Paris Agreement on climate change, humanity is seeking to reduce greenhouse gas emissions and keep planetary heating to no more than 1.5°C above the pre-industrial average. In 2024, temperatures on Earth surpassed that limit.

This was not enough to declare the Paris threshold had been crossed, because the temperature goals under the agreement are measured over several decades, rather than short excursions over the 1.5°C mark.

But the two papers just released use a different measure. Both examined historical climate data to determine whether very hot years in the recent past were a sign that a future, long-term warming threshold would be breached.

The answer, alarmingly, was yes. The researchers say the record-hot 2024 indicates Earth is passing the 1.5°C limit, beyond which scientists predict catastrophic harm to the natural systems that support life on Earth.

2024: the first year of many above 1.5°C

Climate organisations around the world agree last year was the hottest on record. The global average temperature in 2024 was about 1.6°C above the average temperatures in the late-19th century, before humans started burning fossil fuels at large scale.

Earth has also recently experienced individual days and months above the 1.5°C warming mark.

But the global temperature varies from one year to the next. For example, the 2024 temperature spike, while in large part due to climate change, was also driven by a natural El Niño pattern early in the year. That pattern has dissipated for now, and 2025 is forecast to be a little cooler.

These year-to-year fluctuations mean climate scientists don’t view a single year exceeding the 1.5°C mark as a failure to meet the Paris Agreement.

However, the new studies published today in Nature Climate Change suggest even a single month or year at 1.5°C global warming may signify Earth is entering a long-term breach of that vital threshold.

What the studies found

The studies were conducted independently by researchers in Europe and Canada. They tackled the same basic question: is a year above 1.5°C global warming a warning sign that we’re already crossing the Paris Agreement threshold?

Both studies used observations and climate model simulations to address this question, with slightly different approaches.

In the European paper, the researchers looked at historical warming trends. They found when Earth’s average temperature reached a certain threshold, the following 20-year period also reached that threshold.

This pattern suggests that, given Earth reached 1.5°C warming last year, we may have entered a 20-year warming period when average temperatures will also reach 1.5°C.

The Canadian paper involved month-to-month data. June last year was the 12th consecutive month of temperatures above the 1.5°C warming level. The researcher found 12 consecutive months above a climate threshold indicates the threshold will be reached over the long term.

Both studies also demonstrate that even if stringent emissions reduction begins now, Earth is still likely to be crossing the 1.5°C threshold.

Heading in the wrong direction

Given these findings, what humanity does next is crucial.

For decades, climate scientists have warned burning fossil fuels for energy releases carbon dioxide and other gases that are warming the planet.

But humanity’s greenhouse gas emissions have continued to increase. Since the Intergovernmental Panel on Climate Change released its first report in 1990, the world’s annual carbon dioxide emissions have risen about 50%.

Put simply, we are not even moving in the right direction, let alone at the required pace.

The science shows greenhouse gas emissions must reach net-zero to end global warming. Even then, some aspects of the climate will continue to change for many centuries, because some regional warming, especially in the oceans, is already locked in and irreversible.

If Earth has indeed already crossed the 1.5°C mark, and humanity wants to get below the threshold again, we will need to cool the planet by reaching “net-negative emissions” – removing more greenhouse gases from the atmosphere than we emit. This would be a highly challenging task.

Feeling the heat

The damaging effects of climate change are already being felt across the globe. The harm will be even worse for future generations.

Australia has already experienced 1.5°C of warming, on average, since 1910.

Our unique ecosystems, such as the Great Barrier Reef, are already suffering because of this warming. Our oceans are hotter and seas are rising, hammering our coastlines and threatening marine life.

Bushfires and extreme weather, especially heatwaves, are becoming more frequent and severe. This puts pressure on nature, society and our economy.

But amid the gloom, there are signs of progress.

Across the world, renewable electricity generation is growing. Fossil fuel use has dropped in many countries. Technological developments are slowing emissions growth in polluting industries such as aviation and construction.

But clearly, there is much more work to be done.

Humanity can turn the tide

These studies are a sobering reminder of how far short humanity is falling in tackling climate change.

They show we must urgently adapt to further global warming. Among the suite of changes needed, richer nations must support the poorer countries set to bear the most severe climate harms. While some progress has been made in this regard, far more is needed.

A major shift is also needed to decarbonise our societies and economies. There is still room for hope, but we must not delay action. Otherwise, humanity will keep warming the planet and causing further damage.

Andrew King, Associate Professor in Climate Science, ARC Centre of Excellence for 21st Century Weather, The University of Melbourne and Liam Cassidy, PhD Candidate, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

State of the Climate Report 2022 - temperature graphs

(c) BOM/CSIRO

(c) BOM/CSIRO

Sydney's temperatures and increased heat from climate change

                                                                                                  Shutterstock

Extreme weather events have focussed attention on the effect of temperature in large urban centres. None more so than for cities that have large built-up precincts and are subject to urban overheating.

Urban overheating can be caused by multiple factors including building materials (which absorb rather than diffuse solar radiation), human activity and air pollution, dense closed-in areas with little vegetation and few open areas to name a few.  

Research from the University of NSW has found that the mean daily maximum temperature was between 8 and 10.5 degrees Celsius hotter in Western Sydney than the Central Business District (CBD) of the city. Western Sydney was measured as being 20 to 50 kilometres inland.

For the inner suburbs of Sydney, located 8 to 12 kilometres inland from the CBD, the temperature variation was 5 to 6.5 degrees Celsius.  

One reason that has been proposed for this significant heat variation is the proximity of the Sydney CBD to the ocean with coastal breezes cooling the  inner city but unable to penetrate further inland.

Climate change - the challenge of not exceeding a 1.5 degree Celsius increase

                                                                                         Shutterstock

Global management consulting firm, McKinsey & Co, has provided a simple summary of the impact of a 1.5 degrees Celsius increase in temperature and the solutions to prevent crossing this critical threshold. These can be listed as -

Impacts

• weather events become more extreme and frequent. These include wildfires, hurricanes, severe storms, drought, flooding and very high temperatures.
• climate feedbacks occur such that climate change triggers changes on the planet which lead to further changes in the climate and an ongoing cycle occurs becoming self-reinforcing. The higher the temperature, the greater the effect.
• climate feedback include higher temperatures contributing to the loss of forests which in turn lead to the loss of carbon capture, increased carbon release and correspnding higher climate change levels.
• loss of ice cover warms the Earth with less reflective cover from the sun and hence contributes to further temperature increase.
• the current situation where climate change can already been felt is the result of an increase of 1.1 degrees Celsius.

Solutions

• 75% of emissions of CO2 relate to energy production and use so this is a primary focus.
• power companies have been moving away from traditional coal and gas burning and moving to renewables such as solar and wind power. Clean hydrogen or green hydrogen is the new growth opportunity.
• Carbon capture and storage is essential to get CO2 out of the atmosphere. This is best achieved through reforestation since plants absorb carbon. However each year an area the size of Greece is being deforested. McKinsey & Co believe that by 2030, reforestation would need to be the size of Turkey.
• food production is a major source of the greenhouse gas, methane. Cows are the major source of methane although rice production also contributes to this gas. All the cows on the planet currently generate emissions "roughtly on a par with the United States". This can be addressed though various measure such as less beef consumption, changes to certain breeding and genetic selection, methane inhibitors, feed-mix additive changes.
• road transport accounts for around 15 per cent of CO2 with electrification of vehicles seen as a viable solution using green generation source and battery storage being the pathway aways from emissions.
• heating (such as space and water heating associated with buildings) accounts for 5 to 8 per cent of global emissions. The solution is adaption to using green energy sources for power.
• increased efficiency in production and process optimisation in heavy indsutry is a critical related step. Recycling of steel has been identified as a key influence on reducing emissions.

While various initiatives have been taken to commence applying many of these solutions, including most notably in the private sector, concerted support from National Governments is still needed worldwide in order to effect the transition in multiple industries. To do less will lead to unthinkable failure.

Climate change - global temperature rises since 1860

Temperatures since 1860 have increased in heat with considerable movement upward from 1940 onwards with this trend line projected to continue for the next two to three decades unless action is taken to reduce Greenhouse gas emissions.

Climate change - the myth of a hiatus in rising temperatures

Significant anomalies - NOAA

Assertions made in 2006 contending that there was a 'pause' or hiatus in global warming have been restated repeatedly by climate change sceptics for the past few years, particularly when attempting to rebuff the key reports such as the Fifth Assessment Report by the International Panel on Climate Change (IPCC). New data from the United States' National Oceanic and Atmospheric Administration (NAOO) has shown that global temperature change has continued unabated. There is no hiatus.

The year-to-date temperature across global land and ocean surfaces was 1.53°F (0.85°C) above the 20^th century average. This was the highest for January–September in the 1880–2015 record, surpassing the previous record set in 2014 by 0.19°F (0.12°C).

The average Arctic sea ice extent for September 2015 was 720,000 square miles (28.88 percent) below the 1981–2010 average. This was the fourth smallest September extent since records began in 1979, according to analysis by the National Snow and Ice Data Center using data from NOAA and NASA. Below-average sea ice was observed across most regions of the Arctic, while near-average sea ice was observed in the Barents Sea.

The report from the NOAA can be located at the link below:

National Oceanic and Atmospheric Administration Report

Global warming audit - better or worse ?

Global warming - on track for 40C increase and beyond

With the IPCC's latest assessment due out towards the end of this year (and given some of the leaks of the draft report have been manipulated by a climate change sceptic), the question arises of where the world's environment currently sits and forward projections. Looking through the various aspects of the measurement of climate and geoinformation available the trend of serious climate change appears to be unstoppable with the reality that current generations will also experience the effects, first-hand. 

  
Loss of sea ice in the polar regions: sea ice has fallen to its lowest levels for at least 1400 years which means heat reflecting white ice has been replaced by heat absorbing black ice. The effect of this change is more extreme weather events in the Northern Hemisphere, melting of the higher level permafrost and hence the  release of more carbon into the atmosphere and faster melting of the Greenland ice sheet which affects ocean levels.

Extreme weather increases: Russia experienced extraordinary hot temperatures above 400C in 2010, North America (Canada and the US) had the converse with record snow  and rainfall  and superstorm 'Sandy' demonstrated the impact of more extreme weather events. 2012 and early 2013 have followed similar weather trends The warming in the Arctic is believed now to have caused the polar jet stream to have slowed thus reducing the movement of patterns of weather. In this sense storms can  become locked in place.

Falling food production: Global production of staple food stocks such as wheat, maize, rice and soybeans between 1980 to 2008 which were expected to increase, in fact have fallen 1%. Extreme rainfall and extreme heat are considered the likely culprits.

Rising sea levels faster than expected: the Greenland and Antarctic ice sheets have been losing enough ice each year to raise sea levels by 1.3 millimetres per annum which is increasing each year. The expected sea rise is projected at 2 metres which would render many major coastal urban cities vulnerable to flooding and storm surges.

Greenhouse gas levels continue to rise: half of the  CO2 which is emitted is absorbed by land and oceans but with global warming, the capacity for this absorption is reduced and conversely the risk increases of CO2 releases from both may occur instead. The various climate change models which have been used for forecasting did not include the permafrost melting or methane hydrate's being released from the ocean.   

The reality which now underpins all projections of increases in global temperature is that carbon emissions have actually been rising not reducing so the planet is well on course to be between 50C and 60C hotter by 2100 and will reach 40C many years before that.  As yet however the necessary levels of mandatory steps have not been taken as the imperative for immediate action on a greater scale has not been accepted or is being denied. Surely there are few species on the planet that could do more to render their own home uninhabitable.

How hot will the Earth become with Climate Change ?

Various models of climate change provide an indication of what the actual temperature of the planet may reach however, as observed in a number of studies,including those from the Intergovernmental Panel on Climate Change (IPCC) not all factors are included. For example, the impact of melting of permafrost in the Northern Hemisphere and the subsequent release of methane gas is not included yet this may and probably will have a significant impact. The concept of 'hyper-warming' is becoming more of a mentioned consequence which could include a warming of 10 degrees Celsius across the globe. Hyper warming would occur not only due to the release of additional GHG emissions through melting but also would be an effect of the continuous burning of fossil fuels which still continues well above all possible CO2 reduction targets.  The tipping point for climate change remains the magical figure above 2 degrees C yet this will occur regardless so hyper warming may be the end result.

The melting of the permafrost - another risk of climate change

Percolating through seawater

Among the multitude of impacts of climate change, rising temperatures and increased CO2 emissions, one of the other lesser known results is the release of methane from the permafrost regions of the Northern hemisphere. Research in 2010 in the East Siberian Artic Shelf identified methane concentrations eight times higher than the rest of the Artic Ocean and almost a hundred locations of higher methane release. The unlocking of methane in the permafrost, should it occur at a higher rate due to higher temperatures would lead to a warming in the atmosphere which would be impossible to stop.