Climate Indicators

CO2 Concentration

The concentration of carbon dioxide (CO2) in Earth's atmosphere is a critical indicator of our planet's climate health. A stark report by a U.S. scientific body revealed an alarming milestone: in May 2021, CO2 levels reached their highest in 63 years of precise measurement. This concentration is the net result of anthropogenic emissions balanced by the natural absorption by oceans and biosphere. The oceans, Earth’s significant carbon sinks, absorb about a quarter to a third of all CO2 emissions, but the remaining CO2 increases the greenhouse effect, accelerating global warming. This warming is quantified by radiative forcing, a concept explained by the IPCC, which shows a considerable rise in positive forcing from human-induced greenhouse gases, leading to increased energy accumulation on Earth.

Carbon dioxide is responsible for 82% of the increased radiative forcing over the last decade, posing a threat to the UN's Sustainable Development Goal 13 on climate action. From the total energy accumulation, 1% warms the atmosphere, 3% heats the ground, 3% melts ice, and the vast majority, 93%, warms the oceans. This heating leads to ocean acidification, endangering marine ecosystems and undermining SDG 14's goal for life below water. Rising CO2 also affects photosynthesis rates, impacting agricultural output and the nutritional content of crops, thereby posing risks to global food security (SDG 2). Elevated atmospheric CO2 levels may also pose direct health risks, threatening progress toward SDG 3, which ensures healthy lives. Indirectly, CO2 concentration is connected to nearly all 17 SDGs, and reducing emissions is crucial for achieving these global objectives.

Sea Level Rise

Global average sea level rise, now at 3.2 mm per year, presents critical risks to coastal zones, agriculture, and ecological networks. The rising sea levels, exacerbated by increased tropical storms and precipitation, threaten to flood ecosystems, disrupting salinity, temperature, and light levels, potentially drowning flora and fauna. This endangers progress toward SDGs 14 and 15, aiming to conserve life below water and on land. Coastal ecosystems, which protect shorelines and mitigate sea-level rise impacts, have lost nearly 50% of their wetlands in the last century. This loss, combined with human activity, rising sea levels, and increased extreme weather, causes extensive damage to infrastructure, endangers lives, incurs financial losses, and impedes progress on various SDGs.

Sea level rise can displace populations, leading to socio-political fragmentation, and saltwater intrusion into groundwater, contaminating soil and threatening agriculture. These effects undermine poverty reduction (SDG 1) and hunger eradication (SDG 2). Increased risk of waterborne diseases during floods due to rising sea levels can halt advancements in health (SDG 3) and sanitation (SDG 6). The threat of scarcity, reduced food stability, and livelihood loss can lead to conflicts, affecting vulnerable groups more severely, especially those facing socioeconomic and gender disparities.

Glacier Mass Balance

Glaciers are critical for providing freshwater globally and their health is intimately linked with climate changes. Glaciers worldwide, especially in Asia's high mountains and across the Americas, reflect climatic shifts through their mass balance. The 33rd consecutive year of net glacial mass loss in 2020 underscores their vulnerability. Glaciers regulate Earth's climate, and their shrinkage, particularly of Greenland and Antarctic ice sheets, has contributed to one-third of observed sea-level rise. Melting glaciers disrupt ocean currents and reduce the ocean’s CO2 absorption capacity, exacerbating climate change and challenging SDG 13's climate action objectives. Furthermore, changes in ocean circulation could significantly alter global weather patterns, negatively impacting habitats and ecosystems, thus impeding SDG 15's life on land goals.

The diminishing glaciers threaten biodiversity, forcing species to migrate to new habitats. The increased risk of glacial floods and water contamination hinders progress towards clean water and sanitation (SDG 6). Landslides, mudslides, and avalanches from glacier retreat threaten human lives and infrastructure, disrupt transportation, and cause economic losses, hindering progress on multiple SDGs. These disruptions pose a risk to agriculture, threatening food security and livelihoods, thus hampering Sustainable Development Goals.

Ocean Acidification

The increase in CO2 levels is causing significant ocean acidification, posing grave threats to marine ecosystems and human existence. As the ocean absorbs a substantial portion of CO2 emissions, it leads to lower pH levels, affecting marine life, particularly calcifying organisms like coral reefs, pivotal to marine ecosystems. The current rate of acidification surpasses any known change in the last 55 million years. Ocean acidification, explicitly targeted in SDG 14, requires urgent attention to mitigate and understand its far-reaching effects.

Sensitive species like mussels, crabs, and corals are threatened by acidity changes, disrupting the marine food web, central to SDG 14's conservation and sustainable use of oceans and marine resources. The degradation of coral reefs would result in significant cultural and economic losses, impacting tourism and livelihoods related to various SDGs, especially SDG 11, sustainable cities, and communities. Changes in marine biodiversity can decrease fish yields, affecting farmers' livelihoods and food security, intensifying poverty (SDG 1), and leading to hunger (SDG 2), with profound effects on economically disadvantaged and rural populations. The risks to food security and livelihoods may also escalate conflicts over resources, impacting SDG 16, peace, justice, and strong institutions.

Global Mean Surface Temperature

GMST is the definitive climate change measure, influencing extreme weather and biodiversity loss, with implications for sustainable development. As of 2020, the GMST has risen 1.2°C above pre-industrial levels, primarily due to human activities like fossil fuel combustion and agriculture. The GMST influences the frequency and intensity of extreme weather by altering energy and gas movement between the ocean and atmosphere, leading to stronger storms and altered El Niño impacts, causing droughts and floods. These changes affect rainfall, snowmelt, river flows, and groundwater, challenging clean water access (SDG 6).

Extreme weather affects infrastructure, health, property, and community stability, potentially undermining various SDGs. Health risks (SDG 3) arise from environmental disruptions, disease spread, and mental health issues. Scarcity and access issues may lead to displacement, affecting land ownership and social integration (SDGs 10 and 11), and can fuel conflict over resources (SDG 16). The warming planet leads to permafrost thaw and glacier melt, releasing greenhouse gases and challenging climate action (SDG 13). The effects on food security, water scarcity, health, and livelihoods will disproportionately affect those already facing racial, gender, and economic inequalities.

Ocean Heat Content

The ocean's ability to retain heat is vital for climate stability, with 2019 seeing record ocean heat content levels. Thermal expansion from warming water contributes significantly to 21st-century sea level rise predictions. Temperature shifts alter ocean densities, affecting circulation and CO2 absorption, releasing methane from melting hydrates, and challenging climate action (SDG 13). Ocean heat affects marine biodiversity and disrupts global weather patterns, impacting life on land (SDG 15) and below water (SDG 14).

Reduced oxygen levels and expanding oxygen minimum zones stress marine life, with warm periods potentially causing harmful algae blooms, affecting marine biodiversity and human health. Rising temperatures endanger keystone species like coral reefs, affecting natural heritage sites, tourism, and dependent livelihoods, influencing multiple SDGs. Changes in marine biodiversity reduce fishing yields, exacerbate poverty, compromise food security, and may lead to conflicts over dwindling resources, with systemic inequities magnifying these impacts.

Sea Ice Extent

Sea ice extent, crucial for polar regions' climate, affects global meteorological patterns and ecosystems. Uncertainty remains about sea ice behavior in the Arctic and Antarctic, but 2020 saw the Arctic's second-lowest ice levels, with record lows in July and October. Changes in sea ice extent influence the polar jet stream due to temperature differences between the Arctic and tropics. Reduced albedo from melting sea ice accelerates local warming and global warming, creating a feedback loop that hampers climate action (SDG 13).

Sea ice loss threatens species dependent on ice habitats, with implications for global biodiversity and human livelihoods, affecting poverty and hunger (SDGs 1 and 2). New commercial routes from melting ice raise pollution concerns and potential disputes, impacting marine life and peace and justice (SDG 16).