The 1.5 Degree Danger Line

What is 1.5ºC?

World leaders are striving for a global climate change goal of 1.5-degrees Celsius to help alleviate severe climate changes and rising sea levels and reduce oceans' warming and acidification.

The 2015 Paris climate negotiations championed a goal of 2 degrees Celsius, but experts are now saying that goal is not ambitious enough. The Earth is already on track to increase its global temperature by more than 2 degrees Celsius by the end of the century. 

A 1.5 degree Celsius goal is only a half degree from the current standard. However, that difference could mean a reduction in catastrophic storms, extreme weather, and floods.  

Climate-Related Risks When Exceeding 1.5ºC

There is a clear and present threat when the world nears or exceeds the long-term average temperature. The main risks associated with this degree of warming include:

Temperature Extremes

Warm. Extreme temperatures inland are estimated to warm more than the global average surface temperature, with considerable differences from place to place. Most tropical land regions will see more hot days.

Increasing global warming from 1.5 degrees Celsius to 2 degrees Celsius could mean over a billion more people could be exposed to extreme heat waves at least once every five years.  

Millions of people will become exposed to risks associated with climate change.

The hottest days in Earth's mid-latitudes will be up to 3 degrees Celsius hotter at 1.5 degrees warming and up to 4 degrees Celsius warmer at 2 degrees Celsius.

The warmest extreme places will be in Central and Eastern North America, Western and Central Asia, Central and Southern Europe, the Mediterranean, and South Africa.

Cold. The coldest nights in high latitudes on Earth will be warmer, about 4.5 degrees Celsius at 1.5 degrees of warming and warmer at about 6 degrees Celsius at 2 degrees of warming.

With 5.5 degrees Celsius at 1.5 degrees Celsius warming or less, arctic land regions will see cold extremes warm, while at 1.5 to 2 degrees Celsius warming, cold extremes warmer will be up to 8 degrees Celsius.

Droughts

It is expected to significantly lessen the probability of drought and risks related to water availability when warming limits to 1.5 degrees Celsius in some regions, like the Mediterranean, South Africa, Australia, and South America.

In a 2-degree Celsius warmer, more than 61 million people in Earth's urban area would be exposed to severe drought.

Water Availability

By limiting global warming to 1.5 degrees Celsius, up to 20 percent fewer people on Earth may see increased climate change-induced water stress. People in river basins will be particularly vulnerable, especially in the Middle and Near East.

At about 1.5 degrees Celsius warming, between 184 and 270 million fewer people will be exposed to increases in water scarcity in 2050, as predicted.

At the higher temperature threshold, risks for groundwater depletion are also expected to be greater.

Extreme Precipitation

Compared to 1.5 degrees warming, increased heavy rainfalls will be seen in some places at a warming of 2 degrees Celsius, especially in the high latitudes of the Northern Hemisphere, mountainous regions such as the Tibetan Plateau, Southeast Asia, and with higher flooding risks in Eastern North America.

It will also be affected by flooding and increased runoff in the areas of Earth's land. Thus, it is also expected that the heavy rainfall from tropical cyclones will increase.

Impacts of 1.5ºC

As the world warms, the negative impacts will be felt by humans and the natural world in a number of ways.

Biodiversity and Ecosystems

• Loss of Species and Extinction. The 6 percent of insects, 8 percent of plants, and 4 percent of vertebrates will see their climatically determining geographic range decrease by more than half at a warming of 1.5 degrees Celsius. 

Hence, those numbers jump twice the number at 2 degrees Celsius warming.

• Fires, Extreme Weather, Invasive Species. The risks from extreme weather events, forest fires, and invasive species will be higher at 2 degrees Celsius warming than at 1.5 of warming degrees Celsius.
• Biome Shifts. At 2 degrees Celsius warming, about 13 percent of land areas are projected to see one type of biome in their ecosystems shift to another. In comparison, at 1.5 degrees, warming will be about 50 percent more.
• Rainforest and Boreal Forests. Warming of 1.5°C to 2°C will lead to a decrease in rainforest biomass and an increase in deforestation and wildfires.

Ocean

• Sea Levels. The rising sea level will continue even if the temperature increase is limited to 1.5 degrees Celsius as heat already stored in the oceans from human-produced warming causes them to expand.
• Polar Ice Sheets. Over hundreds to thousands of years, instabilities in the Antarctic ice sheet and the Greenland ice sheet inevitable loss could lead to a multi-meter rise of sea level at an increased level of 1.5 to 2 degrees Celsius warming.
• Ocean Temperatures, Acidity, Oxygen Levels. Limiting global warming to 1.5 degrees Celsius would decrease the temperature in the ocean, which will relatively increase ocean acidity and reduce oxygen levels, which present significant risks to marine biodiversity, ecosystems, and fisheries.
• Sea Ice. The Arctic Ocean is predicted to be sea ice-free one summer per century at a warming of 1.5 degrees Celsius. 

It increases at least one ice-free summer every decade at 2 degrees Celsius. The habitats of many organisms will be impacted if there is a sea ice loss at a warming of 1.5 degrees Celsius. 

• Marine Ecosystems. Many marine species' geographic ranges will shift to higher latitudes, new ecosystems will appear, and there will be more damage to marine ecosystems at a warming of 1.5 degrees Celsius. 

Humans

• Heat-Related Illness and Mortality. At a warming of 1.5 degrees Celsius, health-related illness and death will be lower than 2 degrees. Due to the urban heat island effect, cities will experience the worst impacts of heat waves which keep them warmer.
• Vector-Borne Disease. Vector-borne diseases like malaria or dengue fever will cause many people to die; thus, risks increase at 2 degrees warming.
• Food Security. Compared to 1.5 degrees Celsus warming, food security is expected to decrease at 2 degrees.

How Close Are We To 1.5°C?

Human-induced warming has already come to 1°C above pre-industrial levels.

There is a 50% probability that we will surpass the 1.5 degree limit within the next five years. It is predicted that by 2026, there will be a year that will be the hottest ever recorded. 

What Can We Do to Limit Global Warming to 1.5°C?

We must stop releasing greenhouse gasses or adding carbon dioxide into the atmosphere to prevent further warming.

We can reduce our reliance on fossil fuels and switch to renewable energy sources.

We also need to improve our efficiency in how we use energy.

Every sector responsible for greenhouse gas emissions requires rapid reductions to keep the warming goal within 1.5 degrees Celsius.

Final Thoughts

The impact of climate change is experienced by the world already, and we are currently on track to exceed the warming limit of 1.5 ºC.

This would lead to devastating consequences for our planet and its inhabitants.

We need to act urgently to reduce greenhouse gas emissions if we want to avoid these risks and protect our planet for future generations.

Limiting global warming to the safer target below 1.5 ºC is possible, but it requires unprecedented changes.

We must necessarily change the way we use and produce energy, how we transport ourselves and goods, what we eat, and how we manage land.

It's a daunting task, but it's one that we must undertake to protect our planet and its inhabitants.

FAQs

1. What is the difference between one degree and one and a half degrees of global warming?

A half-degree difference could damage at least 70% of coral reefs, but at 2°C, more than 99% would be lost.  

2. Why is it so important to limit global warming to 1.5°C?

Global warming limits to 1.5 ºC are significant because they would help reduce the risks of devastating consequences, such as extreme weather events, rising sea levels, and biodiversity loss.

3. What can we do to limit global warming to 1.5°C?

Urgent actions are needed to reduce greenhouse gas emissions by switching to renewable energy sources and improving our efficiency in using energy.

4. How close are we to one and a half degrees of global warming?

The world has currently warmed by about 1°C since pre-industrial times. Around 2040, the world will reach human-induced global warming of 1.5°C if the current warming rate continues.

5. What are the risks of exceeding 1.5°C of global warming?

If we exceed the one-and-a-half degree limit, the impacts of climate change will be even more severe, including more extreme weather events, rising sea levels, and loss of biodiversity.