What’s in a number? The 1.5°C pathway and how to stop irreversible global warming 

The summer of 2023 brought with it catastrophic weather events, from wildfires in Canada, Australia, and across Europe to lethal monsoons in India and major flooding in the US. In addition, July 2023 saw the warmest three week period on record, with the global temperature temporarily exceeding the 1.5 degrees Celsius (1.5°C) threshold above pre-industrial levels (within observational error). These events put the spotlight back on this magic number, with nations who signed the Paris Climate Agreement under pressure to act. But, why now and why at 1.5°C?

What is the 1.5°C Challenge?

The notion that a rising climate could be catastrophic for all life on Earth first gained momentum in the 1970s, when Yale economist William Nordhaus found that a global temperature increase of 2 degrees Celsius over pre-industrial conditions “would push global conditions past any point that any human civilization had experienced.” His theory was expanded in 1988 by NASA scientist James Hansen, who testified in Congress that there is a direct correlation between the emission of greenhouse gases with rising temperatures, and that failure to curb these emissions “could result in catastrophic climate change, the sea-level to rise, extreme weather, and damage to ecosystems and human settlements across the globe.”


During the 1990s, scientists began further research into this topic, often using 1°C or 2°C as the reference point to study the effects of catastrophic climate change. From here, government strategies used these points of reference as concrete goals, often referencing 1.5°C or 2°C as the point of no return. However, despite these decades of warning, it was not until 2015 that world leaders came together to sign the Paris Agreement, a global initiative to reduce emissions to halt global warming by more than 2°C, but preferably by 1.5°C.

Why is 1.5°C planetary warming a problem?

A number does not fully convey the impact a warmer climate would have, so let’s delve into what would happen and why it would happen.

Weather patterns

Rising temperatures mean ocean temperatures will increase, leading to increased evaporation and more rain, which in turn leads to monsoons and flooding. This same increase in ocean temperatures will mean more hurricanes, since once the ocean reaches 29°C to a considerable depth, the conditions are favorable to storms and hurricanes.


An increase in air temperature will also mean melting glaciers, leading to rising sea levels which will wipe out islands and eat away at coastal cities and villages. On the opposite side, areas with little to no ocean presence will see rising air temperatures devastate crops and evaporate ground water, leading to water and food scarcity. An arid climate and water scarcity will also lead to an increase in wildfires, which will further devastate crops, towns, and forests. The devastation of forests will mean less carbon capture from trees, which in turn will worsen global carbon emissions and increase temperatures further.

Climate refugees

As island nations are swallowed by rising sea levels, arid nations are plagued by a lack of food and water, and many areas are devastated by the increase in natural disasters, the world will see populations turn to panic. There will be a rise in the need for international aid and a huge rise of displaced people and climate refugees seeking safer lands. Worse still, competition for ever-increasingly scarce resources will likely lead to deadly wars, meaning more refugees.

Animal and plant extinction

As habitats are destroyed in flooding, forest fires, and melting ice caps, the world will see a loss of many animal and plant species. Moreover, rising temperatures will kill off many plant and animal species that simply cannot survive in the heat, as well as all the marine life that cannot survive in a warmer sea. This in turn, will mean the death of many food sources for other animals, which will subsequently also lead to their demise (and eventually ours).

1.5°C vs 2°C global temperature increase

During the late 1900s, the aim was to ensure global temperatures did not surpass 2°C, however, as scientific research has progressed it has become clear that at a prolonged temperature gain of 1.5 degrees Celsius over pre-industrial levels, the damage will already become irreversible. If, however, the globe does surpass this mark and reaches 2 degrees Celsius, then the difference would mean:

  • An additional 10 million people will lose their homes to rising seas 
  • An additional 2 million square kilometers of permafrost will be lost 
  • 50% more of the global population will experience water scarcity 
  • 50% increase in species losing half their geographic range 
  • Removal of the 1-per-century limit on ice-free Arctic summers when the sea ice drops below 1 million square kilometers (386,102 square miles). 



How has the 1.5°C climate action plan worked so far?

According to the World Meteorological Organization (WMO), the body in charge of tracking the rise in temperatures, the world is now “more likely than not” to reach 1.5 degrees Celsius or warming within the next five years. Although this setback may not be permanent, it is a clear indication that the world is not doing the work set out in the Paris Agreement.

To turn this around quickly so as not to reach a prolonged period above 1.5°C, governments, corporations, and individuals alike will need to make some rapid changes. This will include shifting to renewable energies through the likes of solar and wind power, reducing carbon emissions, investing in carbon capture technology, reforesting, saving water, and changing global dietary, travel, and waste habits, among other things.


Current global estimates for 2023 allocate an investment of USD 2.8 trillion in energy, with USD 1.7 trillion going to renewables and slightly over USD 1 trillion going to unabated fossil fuel supply and power, of which 15% is to coal and the remainder is for oil and gas. According to a 2023 report by the International Energy Agency (IEA) and the International Monetary Corporation (IFC), in order to return the world to the 1.5°C path, annual investments in clean energy in emerging and developing economies will need to triple from USD 770 billion to USD 2.8 trillion by the early 2030s.”

What steps must we take for the 1.5°C climate action plan to work?

As an individual or business, there is an inclination to feel powerless in moving the world away from the devastating consequences of 1.5 degree Celsius climate change, but this is incorrect. Consumers dictate demand, and if demand reduces then so does production and its emission of greenhouse gasses. That is not to say that consumers alone should be responsible for achieving the needed net zero emissions, but by reducing our carbon footprint and investing in renewable energy and technology, the world has a better chance of making the 1.5°C plan work.

Switch to renewable energies

The production of energy and fuel is the leading cause of the greenhouse gas emissions that cause global warming. By switching and investing in renewables, such as installing solar panels on roofs, individuals and businesses will be helping reach net zero and avoid 1.5 degrees Celsius climate change.


Take AE Solar's best-selling Aurora series, for example. A project with a 1 MW capacity can generate up to one million kilowatt-hours of electricity per year, significantly reducing carbon emissions by more than 1,000 tons per year. This proves the power of renewable energy solutions in curbing climate change and promoting a sustainable future.

Ensure proper home insulation

Ensuring buildings are properly insulated will mean lower energy requirements for heating. This will reduce demand and so remove some reliance on fossil fuels during the transition to green energy. By using solar panels and proper insulation, home and business owners can do their bit for the environment and cut fuel costs.


Use public transport, walk, or cycle

Traditional fossil fuels emit greenhouse gases when extracted and when used. Electronic vehicles (EVs) are a better option but one that still demands energy, which is still predominantly created by fossil fuels — according to the IEA, renewable capacity is only expected to meet 35% of global power generation by 2025, and in many countries this percentage will not be met.

To reduce carbon footprints and stay below 1.5°C, public transport should be heavily subsidized to incentivize its use. Additionally, encouraging people to walk or cycle would mean improvements in health and less need for public health services, which consume lots of energy in the form of hospital heating, lighting, and equipment use.

Make some changes to your diet

Although cutting out or reducing meat and dairy is largely regarded as the best way to eat for the planet, there are alternatives. Eating seasonal, local, and organic food cuts down on food transport and pesticides. This means reduced fuel use, reduced water and soil contamination, and the building of a better and more natural environment for animal and essential bee populations. In addition, reducing food waste is key in battling over consumption and helping the planet get back on track.

Conserve water

Although water is a constant on Earth, with very little change in its availability, 99% of it is unusable by humans and other living things. When we waste water, it goes through sewers and treatment plants, meaning a decrease in the quality of drinking water. The use of agricultural pesticides, meanwhile, contaminates the water sources they filter into. This all decreases the availability of drinking water, which leads to water scarcity and the eventual death of plants, animals, and people.

Consume less

Every time an item is made, such as a garment or phone, a huge amount of water and energy is used and more greenhouse gasses are released into the environment. Reducing consumption and reusing and recycling items are therefore great ways to reduce your carbon footprint.


A summary 

Staying below 1.5 degrees Celsius above pre-industrial levels is of paramount importance for the survival of the planet and our species as we know it. By learning more about the ways to stay under this temperature and investing in technologies, renewable energies, and climate solutions, we can be part of the solution. The achievement of the net-zero greenhouse gas emissions target is a gradual process, requiring concerted efforts from the entire society. As long as we work together, we can extend the path of green development further and better.