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CO2 Concentration

Rising levels of human-caused carbon dioxide emissions are triggering cascading effects around the world. The atmospheric concentration of carbon dioxide is a key indicator of the state of the global climate (a US scientific agency reported monthly average atmospheric CO2 for May 2021 at the highest level since accurate measurement had begun 63 years earlier).


Recent studies have also demonstrated that there may be health risks related to increased exposure to high levels of atmospheric CO2 - threatening progress made on SDG 3, “Ensure Healthy Lives.” In fact, CO2 concentration is at least indirectly related to risks outlined in nearly all 17 of the SDGs, and reducing emissions is therefore necessary to achieve the goals.

The ultimate concentration level is the result of exchanges between the atmosphere, the biosphere, and the ocean - and reflects a balance between sources like human-caused emissions, and the sinks that absorb them. One of Earth's biggest carbon sinks is the ocean, which captures between 25% and 30 % of all CO2 emissions. The CO2 that is not absorbed by natural carbon sinks remains in the atmosphere; as its concentration rises alongside other greenhouse gases, it perpetuates the “greenhouse effect” and accelerates warming processes.

Earth warming is measured through “radiative forcing,” a measure defined by the Intergovernmental Panel on Climate Change (IPCC) as a balance between “positive forcing” such as the greenhouse effect, which contributes to the warming of Earth’s surface, and “negative forcing” that cools the surface. Because human-caused emissions of greenhouse gases are skyrocketing, it is boosting “positive forcing” and energy accumulation on Earth.


CO2 is responsible for 82% of the increase in radiative forcing over the past decade, and the greenhouse effect threatens to undermine the necessary climate action outlined in UN Sustainable Development Goal 13. 1% of this energy accumulation warms the atmosphere, 3% dissipates into the ground, 3% melts sea ice, ice sheets, and glaciers, and 93% is trapped by the ocean.


As CO2 dissolves into the ocean it turns into acid ions and reduces pH, which threatens marine ecosystems (the success of efforts to minimize this is a key indicator of progress on SDG 14, “Life Below Water”). As CO2 concentrations increase, photosynthesis processes speed up - producing agricultural yields in less time. This results in a reduction of grain protein concentration that threatens food security (as outlined in SDG 2, “Zero Hunger”).

Ocean Acidification


Approximately 25% to 30% of all CO2 emissions are captured by the ocean - and whenever CO2 dissolves in water, it turns into acid ions. The acidification of the ocean causes a decrease in carbonate ion concentration, which is necessary for marine organisms like coral to form shells and essential skeletal material. As the ocean absorbs higher concentrations of CO2, it puts marine ecosystems and human life at risk.


Because these organisms form the fundamental basis for many complex marine ecosystems, any threat to their ability to form in turn threatens many other species. In recent decades, ocean acidification has been occurring 100 times faster than in the past 55 million years.


In fact, the process of ocean acidification is unique in that it is the only climate indicator that merits designated space within one of the UN’s Sustainable Development Goals - within SDG 14, the third target spells out the need to minimize and address the impact of ocean acidification, including through enhanced scientific cooperation “at all levels.” There is good reason for this, as the impacts of acidification are far reaching.

When organisms sensitive to changes in acidity like mussels, crustaceans, and corals are in danger, so are other species along the food chain that depend on them. That undermines the overarching goal of SDG 14, which is to conserve and sustainably use the ocean and seas.

Many coral reefs have value beyond their ecosystem services and have been declared UNESCO World Heritage sites. Their demise would be both a significant cultural and economic loss (due to declines in tourism), with implications for many SDGs, not least SDG 11, “Sustainable Cities and Communities.”


In addition, significant changes or losses in marine biodiversity can reduce fishing yields, which can lead to reduced or diminished livelihoods (SDG 1 is to end poverty) and cause food insecurity (SDG 2 is to achieve zero hunger) - particularly in low-income and rural areas. Risks to food security and livelihoods can also have significantly different implications based on gender, potentially undermining work done towards gender equality (SDG 5).


Ultimately, food insecurity and loss of livelihood can also drive conflict, particularly disputes over territory and resources, with implications for SDG 16 (“Peace, Justice, and Strong Institutions”). The international community has become increasingly aware of the dangers of ocean acidification in recent years.

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Despite the adoption of the Paris Agreement on climate change and the establishment of the 2030 United Nations Sustainable Development Goals, significant gaps remain between the scientific and political communities when it comes to understanding how climate change risks cascade through environmental, social, and economic systems.


The World Meteorological Organization has established seven climate indicators to provide a holistic picture of the global climate system, and the risks posed by altering it. The ultimate aim of the indicators is to improve our collective understanding of the complex ways climate change threatens sustainable development - and encourage more drastic and immediate climate action.


The World Meteorological Organization has published a new report on Climate Indicators and Sustainable Development: Demonstrating the Interconnections. Its release coincides with the United Nations General Assembly annual session and the opening on 22 September of the SDG Action Zone, which is dedicated to accelerating action on the SDGs.


The aim of the WMO report is to demonstrate the connections between the global climate and the SDGs, which go far beyond SDG 13 for climate action. It also champions the need for greater international collaboration, which is essential for achieving the SDGs, and for limiting global warming to less than 2 °C or even 1.5 °C by the end of this century

The report is accompanied by a story map. It highlights seven climate indicators whose impacts span the SDGs:

  • Carbon dioxide concentration

  • Temperature

  • Ocean acidification

  • Ocean heat content

  • Sea-ice extent

  • Glacier mass balance

  • Sea-level rise.

"In the face of ongoing climate change, poverty, inequality and environmental degradation, understanding the connections between climate and international development is a matter of urgency.

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Sea Ice Extent


Sea ice extent, or areas where ice concentration is greater than 15%, is the most widely used climate indicator to assess long-term changes in the Arctic and Antarctic regions. This critical indicator impacts weather patterns, marine ecosystems, and food chains.


There is still much that is unknown about sea ice behavior at the two poles, though what we do know is not reassuring: annual minimum sea-ice extent in the Arctic was the second lowest on record in 2020, with record low sea-ice extents observed in July and October. Changing sea ice extent impacts the global climate system through the polar jet stream, which is a type of thermal wind that arises due to a strong contrast between cold, polar air and warm, tropical air.


As the Arctic warms, the temperature differential between that pole and the tropics is reduced, weakening the jet stream and causing warm air to creep north and cold air to plunge south. Another significant impact of sea ice extent on the global climate is reduced surface “albedo,” or reflectivity, which causes faster local warming.

As light surfaces like sea ice become more reflective, more solar radiation bounces back into the atmosphere. The flip side of that is that as sea ice melts, the amount of light surface is reduced and the darker melt water and ocean below absorb more solar radiation.

The result is that sea temperatures and surface air increase, further accelerating warming and the melting of sea ice in a feedback loop. As this change in surface albedo speeds up warming, it undermines progress made on UN Sustainable Development Goal 13, “Climate Action.”


As ice melts and creates fewer blockages, new routes for transportation are becoming available - increasing commercial traffic and possibly further exacerbating pollution in ways that hurt marine life and potentially fuel conflict. In addition, as sea ice melts the species that depend on it - including algae, zooplankton, polar bears and wolves - are placed at risk.


Given the connections across marine ecosystems, changes in Arctic and Antarctic sea ice could have global repercussions, threatening biodiversity in ways that can affect livelihoods, increase poverty, decrease food security for those depending on fishing yields, and undermine several SDGs.

Glacier Mass Balance


Glaciers are distributed across the planet, with concentrations in the high mountain ranges of Asia, and in both North America and South America. Glaciers provide freshwater to millions of people around the world, and their fate is tied to the changing climate. Glaciers have a significant impact on the global climate. In the past decade alone, glacial mass loss (particularly ice sheets in Greenland and the Antarctic) has accounted for nearly a third of the total sea-level rise now being recorded.


Glacial mass balance is defined as the sum of all gains and losses in ice mass - and preliminary data show that 2020 marked the 33rd consecutive year of recording a negative result. As cold glacial water melts into the ocean, it also disrupts the current thermohaline circulation - which in turn reduces the ocean’s capacity to absorb carbon dioxide. Combined with thawing permafrost throughout the Arctic that releases million tons of carbon per year into the atmosphere, glacial mass loss perpetuates climate change and undermines progress made towards UN Sustainable Development Goal 13 - “Climate Action.” In addition, changing ocean circulation could significantly alter weather patterns around the world, putting habitats and ecosystems at risk and hindering SDG 15, “Life on Land.” 

Glaciers are now melting so quickly that they pose an increased risk of floods and contaminated water, hindering SDG 6 (“Clean Water and Sanitation”).

Landslides, mudslides and avalanches can also occur, putting lives at risk and threatening infrastructure including homes and businesses, disrupting transportation, exacting significant economic losses and causing development setbacks, and undermining a number of SDGs.


Biodiversity in particular is at greater risk, as plants and animals are forced to move and establish habitats in new areas as glaciers recede and the snow-free seasons lengthen. These disruptions also risk agricultural yields, threatening the livelihoods of people who depend on them and undermining food security in ways that also hinder efforts related to the SDGs.


Longer term, reduced glacial snowmelt and runoff threaten reliable access to safe, clean, drinking water - and the tourism centered on glaciers, in addition to related cultural services, will be increasingly threatened. It is important to note that many of the risks posed by changing glacial mass will be experienced differently around the world - and will no doubt fall disproportionately on those already suffering from socioeconomic and gender inequalities.

Ocean Heat Content


The ocean covers more than 70% of Earth’s surface and has an incredible capacity to store heat - lending it a central role in stabilizing the global climate system. The ocean’s central role in Earth’s climate system means temperature changes pose serious risks. Ocean heat content reached record levels in 2019. As water warms, its volume increases - and thermal expansion is responsible for between 30% and 55% of sea level rise during the 21st century.


Temperature changes also lead to shifting densities of surface and deep water, reducing ventilation and causing stratification. This reduces the ocean’s ability to absorb carbon. In addition, rising ocean temperatures can cause melting hydrates to release methane (another potent greenhouse gas) into the atmosphere. Increasing ocean heat content therefore directly threatens to undermine any efforts made in line with the UN’s Sustainable Development Goal 13, “Climate Action.”

Changes in ocean heat dynamics are also responsible for Atlantic Meridional Overturning Circulation weakening, which is projected to have a significant impact on weather patterns. Changing weather patterns may cause cascading impacts on ecosystem structure and functioning, affecting species on land and hindering SDG 15, “Life on Land.” 

Ocean circulation slowdown is also a threat to SDG 14 (“Life Below Water”), as it hinders the movement of nutrient content and oxygen to marine organisms. In fact, there has already been a as much as a 3.3% oxygen loss since 1970, and oxygen minimum zones have extended by as much as 8%. Warming, particularly during marine heatwaves and deoxygenation, can also contribute to an increased risk of harmful algae blooms that cause significant impacts to both marine biodiversity and human health.


Ultimately, changes in marine biodiversity can lead to reduced fishing yields, and further threaten livelihoods while expanding poverty, threatening food security, and potentially leading to conflict over increasingly scarce resources. It is important to note that these impacts will have significantly worse implications for those people already affected by socioeconomic and gender systemic inequalities.

Higher temperatures can negatively impact keystone species like coral reefs, for example - and as these reefs are damaged, so too are natural heritage sites, tourism opportunities, and the many livelihoods that depend on them, in ways that undermine multiple different SDGs.

Global Mean Surface Temperature

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Global mean surface temperature (GMST) is the international standard for climate change policy. By 2020, warming was already 1.2°C above pre-industrial levels. Temperature drives extreme events and biodiversity loss with serious consequences for sustainable development.


GMST has a significant influence on the extreme weather events that have become more common; the exchange of energy, momentum, and gases between the ocean and atmosphere causes more severe tropical cyclones and storms and the intensification of El Niño events, leading to drought and floods. GMST also affects the pressure gradient - and therefore wind patterns, jet streams and storm tracks, leading to more frequent and intense cold and heat waves.


Such extreme events will profoundly affect life on land and in the sea, primarily in the form of habitat loss, migratory shifts, and “trophic cascades” (shifts among predators and prey that alter food chains). Biodiversity loss, combined with increased temperatures, extreme events, and water scarcity all put agricultural and fishing yields at risk, undermining livelihoods and food security (with implications for the first two UN Sustainable Development Goals - eliminating poverty and hunger).

 Extreme events also threaten infrastructure in ways that put health at risk, damage property and communities, disrupt transportation, cause economic loss and hinder development - potentially undermining multiple SDGs. Temperature rise and extreme events also distort rainfall, snowmelt, river flows, and groundwater, with implications for SDG 6 - “Clean Water and Sanitation.” 

SDG 3, “Good Health and Well-Being,” is placed at risk, for example, due to social and environmental disruption that can enable disease to spread more easily, and cause significant trauma that impacts mental health. The combination of extreme events, health issues, water scarcity, and food insecurity increases the risk of short- and long-term displacement, undermining work on establishing land rights and promoting social and economic inclusion and labor rights.


It is important to note that these impacts on food security, water scarcity, health, and livelihoods will not be equally felt - those already affected by systemic racism and gender and socioeconomic inequalities will be more significantly affected.


The increased risk of displacement, water scarcity and food security can in turn increase the likelihood of conflict, undermining SDG 16 - “Peace, Justice, and Strong Institutions.” A warming planet also causes permafrost and glacial melt, further undermining infrastructure and releasing greenhouse gases into the atmosphere. This feedback loop undermines any governmental action on climate (SDG 13 is “Climate Action”).

Sea Level Rise

Sea level rise is one of the most important climate indicators, because it reflects many different changing components of the climate system and their interaction. Over the past few decades, global mean sea level has risen approximately 3.2 millimetres per year. Rising sea levels pose significant risks to coastal populations, food systems and ecosystems.


As sea levels rise, extreme events and coastal flooding are more likely to occur - and are likely to be further exacerbated by projected increases in tropical cyclone intensity and precipitation. This can endanger ecosystems, as water temperature and salinity are altered, amounts of available light change, and plants and animals potentially drown in ways that undermine progress made on UN Sustainable Development Goals 14 (“Life Below Water”) and 15 (“Life on Land”).


While vegetated coastal ecosystems can often protect coastlines from storms and erosion, and help buffer the impacts of sea level rise, nearly half of all coastal wetlands have actually been lost over the past century, as a result of the combined effects of localized pressure caused by human activity, rising sea levels, warming, and increasingly prevalent extreme weather events.


These extreme events can damage infrastructure, put lives at risk, cause significant economic losses, and hamper progress made on multiple SDGs. Sea level rise can also displace populations, impoverish them, and fracture them politically. Coastal flooding can cause the salinization of ground water, and result in soil becoming inundated with salt water - contaminating it and harming crops in ways that threaten yields and damage farmers’ livelihoods and food security (SDG 1 targets poverty, while SDG 2 targets hunger, and both may be undermined).


It should be noted that many of the risks posed by sea level rise will be felt disproportionately around by those people around the world already faced with socioeconomic and gender inequalities. The increased risk of water contamination during flooding as a result of sea level rise can undermine progress made on SDG 3, “Good Health and Well-Being,” and on SDG 6, “Clean Water and Sanitation.” This threatened state of access to clean water along with diminished food security and livelihoods create an increased risk of local conflict - potentially further raising the risk of population displacement.

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