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As the human population grows, so does food demand. While famine has been greatly reduced, adequate food supply for all has not been achieved and we are expecting another 1 to 3 billion mouths to feed in the next few decades. Classical agriculture is driving deforestation, and its yields are suffering from reduced soil quality and climate change variability. Could an Aquaponics system be the solution to food insecurity?

What is an Aquaponics System?

aquaponics system

Image source: https://ag.purdue.edu/envision/the-big-idea-hydroponics-aquaponics/ 

Aquaponics is a type of farming system that combines aquaculture (farming of fish in water environment) with hydroponics (growing plants with water instead of soil) in a closed-loop system. The animals provide nutrients in the form of broken down excretions, which allow the plants to grow.

The obvious advantages are the reduced land and fertiliser usage, and weather dependence. The amount of water required is also 90-99% less than that of agriculture. Successful examples are beginning to appear, like the GrowUp Urban Farm in London, committed to help feed and educate its community through aquaponic cultures built in a shipping container. At the University of New Hampshire, students help monitor the aquaponics system built on campus, providing food directly to the campus’ dining service.

Finally, the Canadian company The Growcer helps communities, retailers, and organisations grow produce in the Northern parts of Canada where food accessibility is limited by introducing hydroponic container farms. These containers have up to 3,600 planting slots and can allow up to 140 varieties of produce to grow in the container at once.

The Growcer

Image source: The Growcer www.thegrowcer.ca

You might also like: Ways in Which Vertical Farming Can Benefit Our Environment

Could Aquaponics Systems Help Solve Food Insecurity?

At first glance, the aquaponics system seems like the perfect solution to agriculture’s ails. It can help communities, where agriculture is insufficient to feed the population, become less reliant on imports. The systems can also be located wherever is most convenient, reducing supply chain length and thus food loss during transportation. However, as you may have guessed, there are a few important flaws.

First, the system requires a large amount of energy to run, which may be a problem for many developing countries where resources are scarce. Solutions like direct solar energy supply are feasible, but even  more expensive. Other restrictive features include the need for precise water acidity balance, temperature regulation, algae growth and chemical compound build-up control. The expertise and time required may not be available to places most in need of agriculture solutions.

The aquaponics system is undeniably more economical and resource-efficient when compared to traditional farming methods. The amount of water it saves could be the most significant aspect considering that 70% of all freshwater used by humans goes into agriculture, and looming water crisis.

The technology needs to be optimised to reduce energy, expertise and supervision requirements before it can become a viable source for the global food supply.

This article was written by June Leung and Owen Mulhern. 

You might also like: Global Food Security: Why It Matters in 2023

Permafrost is a permanently frozen layer below the Earth’s surface, consisting of soil, gravel, and sand, usually bound together by ice. Accelerating permafrost thaw is an issue of great concern to the scientific community and, increasingly, the general public. Rising temperatures are disrupting the balanced state of an ecosystem leading to the emission of methane (CH4), a potent greenhouse gas. Without urgent action to curtail the warming of our planet, half of the world’s permafrost could disappear by the year 2100.

What is Permafrost?

The word ‘permafrost’ was coined by Siemon William Muller, an American geologist as a constriction of ‘permanent frost’. It is defined as a ground that remains frozen for at least two consecutive years and is essentially a mixture of rock, soil, sediment, ice, and organic material. Occurring at high altitudes and latitudes, permafrost covers about 24 % of the Northern Hemisphere. The large majority is found in Russia and Canada near and above the arctic circle.

Permafrost is isolated from the atmosphere by a boundary called an “active layer”, consisting of live plants in summer, with added snow in winter. The active layer transfers heat from or to the permafrost. Permafrost holds the largest global carbon reserve, estimated to contain 1,400 billion tons of carbon, nearly double the amount present in the atmosphere.

Permafrost Distribution

There are four ways to describe the distribution of permafrost: continuous, discontinuous, isolated, and sporadic permafrost.  Continuous permafrost represents an area where frozen soil underlies larger than 90 % of the surface. It is usually found in the coldest areas like part of Siberia. Discontinuous permafrost is usually found in an area where frozen soils lie beneath 50 to 90 % of the surface. Southern Hudson Bay, Canada, has discontinuous permafrost. Sporadic permafrost occurs when frozen soils lie behind 10 to 50 % of the surface. In isolated permafrost, the frozen soils underlie below 10 % of the surface.

permafrost map

Fig. 2. Permafrost Distribution. Source: Brown et al. (1997)

Methane and Permafrost

Methane is a natural gas that contains a carbon atom bonded to four hydrogen atoms. Even though methane constitutes only 0.00018 percent of the atmosphere, it is responsible for about one-sixth of the last  few decades’ global warming. Estimates for arctic methane emissions have gone from 0.5 million tons to 3.8 million tons a year in 2006, then up to 17 million tons in 2013. We don’t have solid measurements yet, but we know the phenomenon is gaining momentum as we speak. A study conducted by Knoblauch et al. 2018 reveals that permafrost soils from the Northern pole would generate one gigaton, or 1000 million tons of methane by 2100. 

arctic methane emissions

Fig.4. Methane emissions from thawing permafrost. Source: Yumashev et al. (2019)

What Happens When Permafrost Thaws?

As temperature rises, frozen organic matter is made available for decomposition into CO2 if oxygen is available or CH4 if not. Since these warm the atmosphere in turn, a positive feedback, but also a vicious cycle is triggered.   

permafrost thaw feedback loop

Fig. 5. Permafrost positive feedback loop.

Impact of global temperature on permafrost

Polar and high altitude areas are more sensitive to climate change than the rest of the world. They have been warming at three times the global average rate, as demonstrated by exceptionally intense wildfire seasons and rapid glacier melt. Permafrost loss is less obvious but just as worrisome. A detailed study revealed that, on average, permafrost around the Arctic, Antarctic, and the high mountain warmed by 0.3 °C between 2007 and 2016. 

permafrost temperature increases

Fig. 6. Annual permafrost temperature change for Northern Hemisphere. Source: Biskaborn et al.(2019).

How to Stop Permafrost from Thawing

Permafrost thawing can be controlled by curtailing our carbon footprint, purchasing environmentally friendly goods, and encouraging eco-friendly businesses, regulations, and policies. Other more imaginative methods include:

1. Using Herds of Hoofed Herbivores 

A recent study published by Beer et al. 2020 in the Scientific Reports, a Nature journal reveals the possibility of using hoofed herbivores such as herds of horses, bison, and reindeer, etc. to prevent the thawing of permafrost. According to the authors, “increasing the population density of large herbivores in the Northern high-latitude will increase snow density and therefore minimize the insulation strength of snow during the wintertime”. The animals trample by compacting the snow surface, allowing cold air to reach the ground. 

2. Using Plants

Researchers from the University of Edinburgh are developing a novel research into the potential application of plants in preventing permafrost from thawing. Plant habitats play an important role in regulating the soil temperature. They provide shade for permafrost soil from direct heat of the sun, and their roots eliminate water making them better insulators.

You might also like: Too Hot to Live In: Extreme Temperatures in Pakistan

Arctic Ocean sediments reveal permafrost thawing during past climate warming, retrieved 19 October 2020 from https://phys.org/news/2020-10-arctic-ocean-sedimentsreveal-permafrost.html.
Baert, J.M., Janssen, C.R., Borga, K., De Laender, F., (2013). Migration and opportunistic feeding increase PCB accumulation in Arctic seabirds. Environ. Sci. Technol. 47, 11793–11801.
Beer, C., Zimov, N., Olofsson, J., et al. (2020). Protection of Permafrost from Thawing by Increasing Herbivore Density. Sci Rep 10, 4170.
Biskaborn, B.K., Smith, S.L., Noetzli, J. et al. (2019). Permafrost is warming at a global scale. Nat Commun, 10, 264.
Brown, J., O.J. Ferrians, Jr., J.A. Heginbottom, and E.S. Melnikov, eds. (1997). Circum-Arctic map of permafrost and ground-ice conditions. Washington, DC: U.S. Geological Survey in Cooperation with the Circum-Pacific Council for Energy and Mineral Resources. Circum-Pacific Map Series CP-45, scale 1:10,000,000, 1 sheet.
Knoblauch, C., Beer, C., Liebner, S., Grigoriev, M.N, Pfeiffer, E.M. (2018): Methane production as key to the greenhouse gas budget of thawing permafrost; Nature Clim Change, 8, 309-312.
Permafrost structure, retrieved 24 October 2020 from https://projects.thestar.com/climate-change-canada/nunavut/
Ying, K., Cheng-Hai, W. (2017). Responses and changes in the permafrost and snow water equivalent in the Northern Hemisphere under a scenario of 1.5 °C warming. Advances in Climate Change Research, 8:235e244.
Yumashev, D., Hope, C., Schaefer, K. et al. (2019). Climate policy implications of nonlinear decline of Arctic land permafrost and other cryosphere elements. Nat Commun, 10, 1900.

The last time carbon dioxide levels on our planet were as high as today was more than 4 million years ago. From atmospheric CO2 and sea level rise to global warming and air pollution. Here are 11 interesting climate change facts that most people are not aware of. 

1. We Are Certain We Caused It

The UN’s Intergovernmental Panel on Climate Change (IPCC) kicked off its 2021 report with the following statement: “It is unequivocal that human influence has warmed the atmosphere, ocean and land.” 

How are we so certain? It took a while, but climate modelling is now refined enough to predict how things would go without human influence, within a margin of error. What we are observing today, however, is beyond that margin of error, therefore proving that we have driven the change. 

You might also like: IPCC Climate Report Warns ‘It’s Now or Never’ to Limit Global Warming As 1.5C Becomes More Out of Reach

2. The Last Decade Was the Hottest in 125,000 Years

Most straightforward of our climate change facts: according to the IPCC’s sixth assessment report on the state of our climate, the past decade is likely to have been the hottest period in the last 125,000 years. For about 100,000 years, we have been oscillating between glacial (ice ages) and warmer interglacial periods like the one we currently live in. Yet, this is also the warmest multi-century period we have had in this timespan. 

climate change facts temperature at its highest in 125,000 years

Source: IPCC, 2021.

The vertical bar on the left shows the estimated temperature (very likely range) during the warmest multi-century period in the last 100,000 years, which occurred around 6,500 years ago during our current era called the Holocene. Only around 125,000 years ago, a time prior to the last ice age, might have had higher temperature than the ones we are currently experiencing. Each of these past warm periods were caused by slow (multi-millennial) orbital variations that are not in play today. 

3. The Ocean Absorbs Most of the Heat We Produce

A 2019 study found that oceans had sucked up 90% of the heat gained by the planet between 1971 and 2010. Another found that it absorbed 20 sextillion joules of heat in 2020  – equivalent to two Hiroshima bombs per second. 

ocean absorbing heat climate change facts

The ocean has tremendous volume and heat-storage capacity, which is why some organisms are used to temperatures being quite stable. Of these, coral reefs are particularly sensitive to temperature levels, reason for which many are now dying off

4. CO2 Is At Its Highest in 2 Million Years

Pre-industrial CO2 levels were around 280 parts per million (ppm). Today, we stand close to 420 ppm. 

CO2 over the past 800,000 yearas, NASA climate change facts

Source: NASA.

The most distant period in time for which we have estimated CO2 levels is around the Ordovician period, 500 million years ago.

historic CO2 levels

Source: Descent into the Icehouse.

Once again, the ocean comes to our rescue by absorbing about one-third of the carbon in the atmosphere. Before the industrial revolution, it was actually a source of carbon, and not a sink, but the massive amount of CO2 now in the atmosphere has forced it to start absorbing the gas. 

5. We Are Losing 1.2 Trillion Tons of Ice Each Year

This item on our list of climate change facts can be hard to comprehend because we are dealing with volume beyond our comprehension.

Since the mid-1990s, we’ve lost around 28 trillion tons of ice, with today’s melt rate standing at 1.2 trillion tons a year. To help you put that into perspective, the combined weight of all human-made things is 1.1 trillion tons. That’s about the same weight as all living things on earth

You might also like: Glacial Melting in Greenland Will Raise Sea Level by 10 Inches: Study

6. Air pollution Is Both Good and Bad

It was recently found that air pollution kills more than 9 million people per year. Developing hotspots in south Asia and Africa will be dealing with poor air quality for years to come, but there is a silver lining.

Polluting particles, such as PM10 or PM2.5, which cause adverse health effects similar to those of cigarettes, actually reflect the sun’s heat rather than trap it. We’ve pumped enough greenhouse gases into the atmosphere to warm it by 1.5C already, but fine particles have kept it around 1.1C so far. 

Some have proposed intentionally disseminating particles into the atmosphere to help reflect more sunlight, but potential unforeseen consequences have prevented us from doing so. 

7. Attribution Is Now Possible (Extreme Weather)

We can now attribute natural disasters to human-driven climate change with certainty. This hasn’t always been the case, as a lack of data and refined techniques for detecting attribution made it hard to tell how much we had to do with each extreme weather events. 

We can now say with precision how much likelier we made things like the North American summer 2021 heatwave, which the World Weather Attribution says was “virtually impossible” without climate change as well as the Indian heatwave, which experts believe it was made 30 times more likely because of climate change.

You might also like: The Key Takeaways From This Summer’s Heatwaves

8. Global Warming Is (Partially) Reversible

If global net emissions were entirely ceased, the warming we’ve caused would gradually reverse but other climate-induced changes would continue for decades if not centuries. For example, sea level rise would probably take millennia to reverse its course. 

if we stopped using fossil fuels and other scenarios

Source: Carbon Brief.

9. We Lost 302.4 Billion Work Hours to Excessive Heat In 2019

If you have ever been in humid South East Asia on a hot August day, you will know that working outdoors with shade is barely feasible, and without, simply dangerous. A report from The Lancet found that the number of work hours lost to heat across the globe increased from 199 billion in 2000 to 295 billion in 2020. That is equivalent to 88 work hours per employed person. 

workk hours lost to heat climate change facts

Of course, daytime outdoor labor is most exposed, which often targets lower-income areas and professions, especially agriculture.

interesting climate change facts

Potential labour lost due to heat-related factors in each sector (1990–2000) Low HDI (A), medium HDI (B), high HDI (C), and very high HDI (D) groups (2019 HDI country group). HDI=human development index. Source: The Lancet

You might also like: The Tipping Points of Climate Change: How Will Our World Change?

10. It Could Become Too Hot to Live in Many Places By the End of the Century

This may the most catastrophic of our climate change facts. As of now, only 0.8% of the planet’s land surface has mean annual temperatures above 29°C, mostly in the Sahara desert and Saudi Arabia (solid black in the map below).

A study by Xu et al. (2020) called “Future of the Human Niche” found that by 2070, under a high emissions scenario, these unbearable temperatures could expand to affect up to 3 billion people (black hashes).

too hot to live climate change facts

Source: Xu et al. 2020, Future of the Human Niche.

Lost work hours are only one example of the impacts of extreme heat, especially  when sustained over long periods. Others include agriculture yield losses, the spread of disease-carrying mosquitoes, and the increased need for air conditioning with its accompanying energy consumption.

11. The Cost of Inaction is Higher Than the Opposite

On the current path, climate change could end up costing us 11 to 14% of the global GDP by mid-century. Regression into a high emissions scenario would mean an 18% loss, while staying below 2°C would reduce the damage to only 4%. 

It has been proposed that ending climate change would take between $300 billion and $50 trillion over the next two decades. Even if $50 trillion is the price tag, that comes down to $2.5 trillion a year, or just over 3% of the global GDP. 

You Might Also Like: Best Places to Live to Avoid Climate Change

Climate change is an incredibly complex phenomenon, and there are many other things happening that were not covered above. If you want to learn more, please visit our data visualization page!
energy storage battery storage

Why this Metric

Fossil fuels pick up the slack when renewables can’t meet demand, either because of bad weather conditions or insufficient capacity. This is why energy storage is a crucial component for a sustainable future, as it counterbalances renewable energy’s intermittent nature. 

Battery storage capacity additions hit 5 GW in 2020, up 50% from a “mediocre” 2019 and enough to power 3.75 million homes. Bloomberg NEF predicts that the global energy storage market will grow 20-fold by 2030, hitting the one terawatt-hour mark with China and the U.S. leading the charge. 

Still, according to the IEA, it isn’t enough to align with the Net Zero Emissions by 2050 scenario. 

Exploring the Metric

Energy storage isn’t just about making up for wind and solar intermittency: it opens a range of solutions for smart grids that can make the overall system more efficient and resilient, regardless of the generation sources. As an example, machine learning could help better predict energy demand patterns and prepare accordingly. 

As of today, China, Europe and the U.S. are leading the energy storage market’s rebound after a paltry year in 2019 where new installations failed to rise for the first time in a decade. Total capacity stood at 17GW worldwide by the end of 2020, and overall investment increased by 40% to USD 5.5 billion. 

Where the Numbers Come From

Data for our figure was sourced from the IEA’s 2021 Energy Storage report.

Future outlook

National policies will widely dictate the sector’s growth, as new solutions that require broad changes are rarely considered before governmental greenlights and incentives are given. The U.S. and China have been mandating targets for energy storage installation, which is why Bloomberg NEF expects them to claim over half the global installations by 2030.

Other countries making big pushes are India, Australia, Germany, the U.K. and Japan. Regions like the Middle East and Africa lag behind, but we can expect them to catch up as renewables penetrate their markets.

Customer-sited batteries will also grow, responding to a desire to consume self-generated solar power in business and homes. This could be an interesting development, especially if subsidized by local authorities – a U.S. federal study revealed that if Americans installed solar panels on every roof, it would supply 39% of the country’s total electricity. 


This article was written by Owen Mulhern. Cover photo by Danilo Alvesd on Unsplash.

Check out our other indices here. 


global sea level rise

Why this Metric

Global sea levels have risen by 21-24 centimetres (8-9 inches) since 1880. At that rate, we’d only be in for another 8 centimetres by 2100, but sea level rise has accelerated. Standing around 1.4 millimetres per year throughout the twentieth century, it more than doubled to reach 3.6 millimetres per year between 2006 and 2015.

Even if we followed a low emissions pathway from today on (which is unlikely), global sea levels would probably rise at least 30 centimetres above 2000 levels by 2100. Conversely, if we follow a high emissions pathway, the worst-case scenario would mean sea levels 2.5 metres above 2000 levels. 

Exploring the Stat

Sea level rise’s acceleration is due to both faster ice melt from glaciers and ice sheets and thermal expansion of seawater as it warms. Higher background water levels mean that storm surges push farther inland than they normally would, increasing the damage caused by events like Hurricane Katrina. Many spots along the U.S. coastline are also experiencing 300% to 900% more high-tide floods than 50 years ago; less deadly than hurricanes but still disruptive and expensive.  

It is important to remember that the rise is not uniform around the world, and two different places at the same elevation may not be equally threatened. Jakarta, for example, is subsiding due to excessive groundwater extraction, making it extremely vulnerable to floods. Thermal, gravitational and wind dynamics can also make localized sea level rise faster than the global average.

jakarta sea level rise

In the near future, ports could also be compromised by the combination of rising sea levels and extreme weather. Key hubs in the Mediterranean, Arabic Peninsulas and South East Asia could be severely disrupted, left with a choice of adapting or displacing their infrastructure. The hit to shipping commerce, which represents 15% of global GDP, would be immense.

How We know

Sea levels have been monitored since the 18th century with tide gauges, and since the early 1990s with satellite altimetry. The relative contribution of thermal expansion was determined largely thanks to a fleet of aquatic robots, while that of ice melt is calculated with both on-site measurements and satellite-detected gravity shifts caused by water moving from land to ocean. 

Future Outlook

How much sea level rise we face will depend largely on the rate of future greenhouse gas emissions. The biggest risk factors are tipping points in the polar ice systems, or thresholds past which they become committed to a large amount of ice loss, no matter our actions from then on. Because we don’t know when the tipping point might be reached, taking a safer approach and assuming it is right around the corner is best. 

Many of the most vulnerable areas in the world are slowly erecting defences against sea level rise such as dykes, sea walls, and better water evacuation. However, most remain terribly unprepared, especially for the fact that the defences they built are likely to be overcome within 20 to 50 years. 

For some, like Jakarta, the only option is displacement. How its 10.5 million inhabitants will do so remains to be seen, and the world will be watching. 


This article was written by Owen Mulhern.

Check out our other indices here.


Why this Metric

Air and water are the quintessential elements to life on Earth. Yet today, over 90% of the population breathes unsafe levels of pollutants, and four billion people experience severe water scarcity for at least one month a year. Of these four billion, 1 billion live in India and another 0.9 billion in China. 

Major cities around the world, like Cape Town, Beijing or Chennai have faced “Day Zero”, the day the tap runs dry. 17 countries, home to a quarter of the world’s population, face “extreme water stress”, according to the World Resources Institute’s (WRI) Aqueduct Water Risk Atlas, whose data we have mapped above. 

Exploring the Metric

Water is essential for food production, electricity generation, manufacturing, and many other cogs of human society. What does water stress look like? In large cities, its residents standing in line for hours to get water from government tanks, and covid-reminiscent shutdowns of many commercial activities. 

In unstable regions like that of the Sahel (the southern border of the Sahara), water stress can lead to, and exacerbate food insecurity and conflict. In Somalia for example, drought forced rural communities to sell off more livestock than usual, leading to a drop in prices and plummeting rural incomes. Poverty incentivizes illicit activities and extremism, which fuelled the rise of terrorist groups like Al Shabaab whose fighters are offered cash revenue. 

In addition to drought, many draw water from untreated, dangerous sources that put them and their children at risk of disease. The World Health Organization estimates that ~3.6 million people, 2.2 million of which are children, die from water-related disease each year. 

Where the Numbers Come From

The WRI’s Aqueduct tool was built off a number of data sources, including  academic papers, WHO reports, hydrological modelling and remotely sensed (satellite) information. 

It is all compiled into a set of freely available resources, including the Aqueduct Water Risk Atlas, Aqueduct Food, Aqueduct Floods, and Aqueduct Country Rankings, designed for decision makers, private entities and the general public.

Future Outlook

Higher temperatures widely modify the Planet’s water cycle, especially in the atmosphere. For every 1°C it warms, its water-carrying capacity increases by 7% (according to the Clausius-Clapeyron relation). The current consensus is that this will make droughts drier, floods wetter and both more frequent. 

UNICEF reports that some 700 million people could be displaced by intense water scarcity by 2030, projecting it to be one of the main drivers of future climate migration. Farmers in Honduras and Guatemala are already mass migrating north to escape crop-killing droughts, hurricanes and hunger. 

With the world tilting toward protectionism and closed borders, these people are unlikely to be given safe haven, meaning they’ll end up in massive refugee camps where they’ll remain exposed to the elements, hunger and disease. 

Water filtration technologies are improving and becoming more accessible, providing a small amount of relief. If developed countries start honoring their climate funding promise, those at risk could make some headway on better infrastructure and water stewardship. This issue will come down to international help and whether we start thinking as a global community. 


This article was written by Owen Mulhern. 

Check out our other indices here. 

plastic production eo indexes

Why this Metric

Plastic is lightweight, durable, cheap and can serve many purposes; we rarely go a day without seeing any. The plastic we now produce each year weighs as much as 2/3rds of humanity’s total mass. Around 300 million tons of plastic are thrown out annually, ending up in landfills or oceans where they linger for decades, centuries and even millenia.

Plastic pollution is so extensive, microscopic pieces have been found in the air, at the top of mount Everest, at the bottom of the ocean and, yes, even inside us. Why should you care? Because it is killing wildlife, vandalizing the beauty of nature and harming us too.  


Exploring the Stat

Bakelite, the first commercially available plastic product, was launched in 1907 but mass production didn’t start until 1952. Since then, annual plastic production has increased nearly 200-fold, peaking in 2019 with 368 million tonnes and leveling off since. 

The world used to ship most of its plastic to China, unconcerned about where it would end up next. However, in 2017, the Chinese government passed the National Sword policy and effectively banned wanton plastic import. Since then, many rich countries have found themselves with far more plastic than they can handle, and recycling has not massively improved. 

Plastic accumulation in nature eventually works its way back to us, either through food or drink. The effects of ingested plastic on the human body has yet to be properly assessed, but it likely causes irritation, inflammation, and possibly carries toxins. 


Where the numbers come from

A landmark study in 2015, led by Roland Geyer, identified and synthesized dispersed data on production, use and end-of-life management of polymer resins, synthetic fibers and additives to produce the first global estimate of all plastic ever produced. 

There are also estimates from private research, such as the data produced by Statista.


Future Outlook

Making new plastic is far cheaper than recycling it, which is why only 9% of all plastics ever get recycled. Similar to the energy transition, it will require government intervention to readjust incentives and allow recycling to gain momentum, attract investment and become more optimized. Right now, environmental damage is shrugged off as an externality and doesn’t strike institutions as a financial loss. 

As evidence of the detrimental effects of plastic pollution grows, more arguments will be available to usher in new legislation. In the meantime, hundreds of thousands of marine animals either die or suffer from plastic, while humans ingest a credit card’s worth each year and don’t even realize. 

This article was written by Owen Mulhern. 


Check out our other indices.

arctic sea ice eo index

Why this Metric?

The arctic has warmed well over twice the average global pace, resulting in more sea ice melt than expected. There are a few ways to measure this, but the main method is by monitoring sea ice extent, or the oceanic area with at least 15% ice cover. Sea Ice extent hit record lows in summer 2012, summer 2019 being the runner-up. The 13 worst years for Arctic sea ice came in the last 13 years, and in 2021, its summer extent was 7.4% lower than the historical average. 

Exploring the Stat

Losing ice has multiple side-effects. The first and most obvious is sea level rise, which has been accelerating and could reach 1 to 2 meters by the end of the century. Second, white surfaces help reflect sunlight into space and keep the planet cool. Its disappearance helps accelerate warming, which melts it faster, creating a feedback loop. Darker waters in the Arctic also absorb more heat. Scientists expect ice free summers could arise as early as 2035 as the system tips toward runaway melt.

The effects on wildlife are already being observed. Sea ice is extra real estate for polar bears and walruses to find food, and hunger-driven bears have drowned during ambitious, but desperate swims. 

Future Outlook

As sea ice disappears, nations prepare to capitalize on new shipping routes, fishing zones, fossil fuel exploration and military activity in northern waters. However, as this develops, walruses and polar bears will lose their habitats, and the warm-weather jetstream will weaken, potentially altering European weather for centuries to come.

This article was written byu Owen Mulhern. 

Check out our other indices here.

extinction eo Index

Why this Metric

Humans have taken over the world, and some say we’ve entered the Anthropocene or the era of man. Half the world’s habitable land is now used for agriculture, doing away with the forests, grasslands, shrubbery and other natural habitats that used to be. 

The IUCN Red List keeps track of known species populations and has estimated the number of extinctions since 1500. They estimate that about 900 species have disappeared for good and that 35,765 species are threatened with extinction today. Another study led by Gerardo Ceballos claims that extinction rates are 100 to 1000 times higher today than the baseline extinction rate (around 1 species per million per year).  


Exploring the Metric

To understand the importance of this topic, we need to understand what would happen if biodiversity truly collapsed. Rich ecosystems depend on their biodiversity, and we depend on the ecosystems. The services they provide are priceless, though if we were to put a price on them, it would be US$16-54 trillion according to Robert Costanza

As for the extinction rate itself, there are a few caveats. Our knowledge of the natural world is far more limited than one might think: we’ve identified an estimated 80% of animals such as birds, mammals and amphibians, but only 1% of insects, and less than 1% of the world’s fungi. Further, the IUCN Red List has assessed only 6% of described species. These two facts together mean that the number of identified threatened species is likely far lower than the actual number. 

Conversely, Ceballos’ findings compare the base extinction rate (2 species per 10,000 per 100 years (E/MSY)) to the amount of recorded extinctions since 1500. He found that these were 100 times higher than the baseline rate. Considering there were probably far more extinctions than those recorded, the estimate is very conservative. 


Future Outlook

Many have claimed that we are at the dawn of the 6th mass extinction. First, let us remind you that mass extinctions in the past wiped out 75% to 95% of all species, usually over the course of thousands of years. 

This makes it perfectly plausible that we are witnessing the start of a new, human-induced extinction episode. Whether or not this is the case, time will tell, but one thing is clear. Were ecosystems to collapse, no amount of bailouts would make up for the lost services they’d have provided. This problem enters the realm of serious existential crises that humanity will face a number of over the next few centuries. 


Editor’s note: We left out the “Where the numbers come from” section you’re used to because methods are a core part of the discussion. If you wish to do some further reading, the IUCN’s methods are available here.

This article was written by Owen Mulhern. 


You might also like: EO Indexes: Longer Summers.


As the second most abundant greenhouse gas in our atmosphere (after water vapor), carbon dioxide (CO2) has become a direct proxy for measuring climate change. Its levels have varied widely over the course of the Earth’s 4.54 billion year history, partly driving swings in our planet’s average temperature.

The History of CO2

Scientific consensus today describes our atmosphere’s evolution in three stages. Around the time of Earth’s formation, our solar system was dense with helium and hydrogen which bounced around the Earth’s surface at extremely high temperatures. These molecules eventually escaped into space and were replaced by our second atmosphere: volcanic emissions. Eruptions dispersed water steam, CO2, and ammonia (one nitrogen and three hydrogens), forming a gassy blanket above and water bodies below. CO2 slowly dissolved into the shallow ocean and allowed cyanobacteria to perform oxygen-emitting photosynthesis. 

This oxygen eventually accumulated until the atmospheric composition changed enough to kill off most micro-organisms present at the time, about 2.4 billion years ago.

CO2 and Past Climates

As a point of reference, pre-industrial CO2 levels were around 280 parts per million (ppm) and today, we stand near 420 ppm. 

The most distant period in time for which we have estimated CO2 levels is around the Ordovician period, 500 million years ago. At the time, atmospheric CO2 concentration was at a whopping 3000 to 9000 ppm! The average temperature wasn’t much more than 10 degrees C above today’s, and those of you who have heard of the runaway hothouse Earth scenario may wonder why it didn’t happen then. Major factors were that the Sun was cooler, and the planet’s orbital cycles were different.

Historic CO2 levels

CO2 levels over the past 500 million years. Foster et al – Descent into the icehouse.

CO2 levels are determined by the imbalance between carbon sequestration (burial in sediments, capture by plants), and carbon emissions (decomposition and volcanic activity). Imbalances in this system created a downward trend in CO2 levels, leading to a glaciation period around 300 million years ago. This was followed by a period of intense volcanic activity, doubling CO2 concentration to about 1000 ppm. Levels then dropped until they reached today’s concentrations during the Oligocene era, 33 to 23 million years ago, when temperatures were still 4 to 6 degrees C higher than today. It can be said that history was shaped by CO2 levels, and the types of climates they would allow. 

Historical temperature data

Temperature estimates over the past 500 million years. By Glen Fergus.

This is quite a worrying fact as the amounts of greenhouse gases we’ve emitted could already potentially take us back to similar conditions.

CO2 Data from Ice Cores

It is undeniable that the climate is an extremely complicated system with many factors that we still do not quite understand, so such statements need to be taken with a grain of salt. Moreover, the further we look back, the more uncertainty there is around the data. Robust evidence “only” spans back 800,000 years thanks to ice cores providing high-resolution records in the form of air bubbles trapped under the freezing snow. 

Ice core CO2 data past 800 000 years

Robust CO2 data from ice cores covering the last 800,000 years. From climate.nasa.gov

The Highest Levels of Co2 in Recent History

We use this record as a baseline to compare current events to, and the post-industrial upward trend in CO2 concentrations is evident. Unfortunately, the trend is recent enough that the results have yet to fully kick in. The time lag between CO2 emission and their pollution and warming effect is around 50 years, and whatever changes we observe now are only the tip of the iceberg. 

Looking back at the 2 extra degrees of warmth last time CO2 levels were this high (Pliocene era, 3 million years ago), should be enough of a call to action considering the damage two more degrees would cause today.

This article was written by Owen Mulhern. 

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