Slow signals
Some of the most important changes can only be measured slowly: emissions are added up from national energy statistics, seawater is sampled from research ships, instruments on the sea floor are read out when a ship recovers them, species are reassessed one group at a time, and harvests, forests and blossoms can only be counted once a year. The indicators on this page are updated once a year or less often, so their latest value is often a year or two old. That is how these measurements work, not a sign that the page has stopped updating. Each section says how far the data reach, how often new data are published, and when new data last arrived here. The sources are checked every week.
Fossil CO₂ emissions
Carbon dioxide released each year by burning coal, oil and gas, by cement production (limestone gives off CO₂ when it is heated) and by flaring gas at oil wells, in billions of metric tons of CO₂. The world total includes international shipping and aviation. Not included: CO₂ from deforestation and other land-use change, which adds roughly another tenth. News reports of the Global Carbon Budget usually quote a slightly lower figure: that headline number subtracts the CO₂ that cement and concrete slowly reabsorb from the air over their lifetime, roughly 0.8 billion metric tons a year. This page shows emissions before that subtraction, so both numbers are correct; they measure slightly different things. These are the emissions that drive the rising CO₂ in the air (see the CO₂ page). Data: Global Carbon Project, fossil CO₂ emissions dataset (Andrew and Peters), the data behind the yearly Global Carbon Budget, published on globalcarbonbudget.org and Zenodo (the version used is named in the line above the chart).
Ocean acidification
The ocean takes up about a quarter of the CO₂ we emit. Dissolved CO₂ forms carbonic acid, so seawater slowly becomes less alkaline: its pH falls. The lower the pH, the more acidic the water. Seawater is still alkaline (above pH 7); "acidification" describes the direction of change. pH is a logarithmic scale, so a small step is a big change: a drop of 0.1 means about 26% more hydrogen ions, the particles that make water acidic. Shown: surface water (0–30 m) at Station ALOHA, 100 km north of Oʻahu, sampled by research ship about once a month since 1988. Dots: pH calculated from the measured carbon and alkalinity of each sample (the full record); measured directly where available. Line: the straight-line trend. Data: Hawaii Ocean Time-series, University of Hawaiʻi (Dore et al. 2009, updated), hahana.soest.hawaii.edu/hot.
Atlantic overturning circulation (AMOC)
The AMOC carries warm surface water north in the Atlantic and cold deep water back south; it keeps northwestern Europe milder than other places at the same latitude and affects rainfall patterns on both sides of the Atlantic. The RAPID array measures it at 26.5°N with moorings across the whole Atlantic, from Florida to Africa, combined with a cable measuring the Florida Current and satellite winds. Strength is in sverdrups (1 Sv = 1 million cubic meters of water per second). Shown: monthly means and the 12-month average. Data: RAPID-MOCHA-WBTS AMOC monitoring project (NOC, University of Miami, NOAA), rapid.ac.uk.
Extinction risk: the Red List Index
The Red List Index follows how the extinction risk of whole groups of species changes over time, based on the IUCN Red List. It runs from 1 (every species in the groups is of Least Concern) to 0 (all extinct). It only counts genuine changes in status, not changes caused by better knowledge, so a falling line means species really are moving closer to extinction. It is based on the groups that have been fully assessed more than once, such as mammals, birds, amphibians, corals and cycads. Data: IUCN and BirdLife International, via the UN Sustainable Development Goals database (indicator 15.5.1, unstats.un.org/sdgs/dataportal).
Tree cover loss
Area where tree cover was removed or destroyed each year, mapped from Landsat satellite images at 30 m detail, in millions of hectares (1 hectare is 100 × 100 m, about one and a half soccer pitches; a million hectares is 10,000 km²). This is gross loss: it counts every stand of trees that disappears, including wood plantations that are harvested and will regrow, and trees burned in wildfires, which may recover. It is not the same as permanent deforestation, but it shows how much tree cover is being lost, where and why. The part caused by wildfires is shown separately. From 2011 the satellite mapping method was improved, so earlier and later years are not fully comparable. Data: University of Maryland (Hansen et al.) and Global Forest Watch, "tree cover loss by dominant driver", via Our World in Data.
Crop yields
Average harvest per hectare worldwide for the four crops that provide most of the world's calories and protein, in metric tons per hectare (1 hectare is 100 × 100 m, about one and a half soccer pitches). The second chart shows each year compared with its own trend (the average of the three years before and after it), so the long upward climb is taken out and good and bad harvest years stand out. Data: FAO, FAOSTAT, crops and livestock products (fao.org/faostat).
Cherry blossom in Kyoto, since 812
The day the mountain cherry trees in Kyoto were in full bloom, one of the longest records of nature's calendar anywhere. Early dates come from court diaries, chronicles and poems describing cherry blossom viewing parties; since the late 19th century from newspapers and observations. Many years before 1400 are missing. The line is the 50-year average (shown where at least 20 years in that window have a date). Kyoto is also a large city, which has warmed more than its surroundings, so part of the recent shift comes from the city itself; the rest follows the wider warming of spring in Japan. Data: compiled by Yasuyuki Aono (Aono and Kazui 2008; Aono and Saito 2010), kept up to date by the cherry blossom prediction competition at George Mason University.