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Abstract

A long-term record of global mean surface temperature (GMST) provides critical insight into the dynamical limits of Earth’s climate and the complex feedbacks between temperature and the broader Earth system. Here, we present PhanDA, a reconstruction of GMST over the past 485 million years, generated by statistically integrating proxy data with climate model simulations. PhanDA exhibits a large range of GMST, spanning 11° to 36°C. Partitioning the reconstruction into climate states indicates that more time was spent in warmer rather than colder climates and reveals consistent latitudinal temperature gradients within each state. There is a strong correlation between atmospheric carbon dioxide (CO2) concentrations and GMST, identifying CO2 as the dominant control on variations in Phanerozoic global climate and suggesting an apparent Earth system sensitivity of ~8°C.

Global average surface temperatures shattered all-time records in 2023 at 1.45 ± 0.12 °C above pre-industrial levels (WMO 2024). Worsened by climate change-induced drought, Canadian wildfires burned 18.5 million hectares, nearly three-times more land area than in any previous year on record (NRC 2023). Parts of the Amazon River reached their lowest levels in 120 years of data-keeping and, in places, recorded surface water temperatures near 40 °C (Rodrigues 2023). The world has reached the threshold of a 1.5 °C increase in global average surface temperature and is only beginning to experience the full consequences.

Methane (CH4) is the second most important anthropogenic greenhouse gas after carbon dioxide. It contributed 0.5 °C of warming in the 2010s relative to the late 1800s—two-thirds as much warming as CO2 (IPCC 2021). It is also far more potent than CO2 ton for ton, with a global warming potential (GWP) >80 and 30 times more than CO2 for the first twenty years and century after release, respectively (Forster et al 2021).

Methane is rising faster in relative terms than any major greenhouse gas and is now 2.6-fold higher than in pre-industrial times. Global average methane concentrations reached 1931 parts per billion (ppb) in January of 2024 (Lan et al 2024). Annual increases in methane are also accelerating for reasons that are debated. Global methane concentrations rose by 15, 18, 13, and 10 ppb each year from 2020 through 2023, respectively, the second, first, fourth, and fourteenth largest increases since the U.S. National Oceanic and Atmospheric Administration (NOAA) methane time series began in 1983 (Lan et al 2024).

The Global Carbon Project updates its Global Methane Budget (GMB) every few years (Saunois et al 2016, 2020, 2024). The GMB integrates results of: (1) bottom-up (BU) estimates based on process-based models for estimating wetland surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations, and (2) top-down (TD) CH4 emission estimates based on atmospheric observations and an inverse-modeling framework. Here, we summarize new estimates of the GMB based on the new GMB (Saunois et al 2024). We estimate CH4 sources and sinks for the periods 2000–2002 and 2018–2020, as well as for the most-recent year (2020), the last year that full global TD and BU methane datasets are available. We compare 3 year-average estimates to smooth the inter-annual variability signals from climatic variability such as the El Niño-Southern Oscillation (ENSO) that influence natural emissions from wetlands and other ecosystems, as well as from the chemical sink.

We provide insights on data for methane sources and sinks globally and for the geographical regions and economic sectors whose emissions have changed the most since 2000. We also provide additional data on changes in recent years using satellite-based inversions using the TROPOspheric Monitoring Instrument (TROPOMI) (e.g. Yu et al 2023).

Highlights

• Climate data from the atmosphere-only HadAM3P model were used to estimate the risks of climatic extreme events in the global breadbaskets.
• To analyse the risks of simultaneous breadbasket failure, the copula methodology was applied.
• Projected wheat, maize and soybean yield losses in the global breadbaskets increase disproportionately between 1.5 and 2 °C global warming.
• The highest simultaneous climate risk increase in the breadbaskets between the two warming scenarios was found for wheat, followed by maize and soybean.

Abstract

The increasingly inter-connected global food system is becoming more vulnerable to production shocks owing to increasing global mean temperatures and more frequent climate extremes. Little is known, however, about the actual risks of multiple breadbasket failure due to extreme weather events. Motivated by the Paris Climate Agreement, this paper quantifies spatial risks to global agriculture in 1.5 and 2 °C warmer worlds. This paper focuses on climate risks posed to three major crops - wheat, soybean and maize - in five major global food producing areas. Climate data from the atmosphere-only HadAM3P model as part of the “Half a degree Additional warming, Prognosis and Projected Impacts” (HAPPI) experiment are used to analyse the risks of climatic extreme events. Using the copula methodology, the risks of simultaneous crop failure in multiple breadbaskets are investigated. Projected losses do not scale linearly with global warming increases between 1.5 and 2 °C Global Mean Temperature (GMT). In general, whilst the differences in yield at 1.5 versus 2 °C are significant they are not as large as the difference between 1.5 °C and the historical baseline which corresponds to 0.85 °C above pre-industrial GMT. Risks of simultaneous crop failure, however, do increase disproportionately between 1.5 and 2 °C, so surpassing the 1.5 °C threshold will represent a threat to global food security. For maize, risks of multiple breadbasket failures increase the most, from 6% to 40% at 1.5 to 54% at 2 °C warming. In relative terms, the highest simultaneous climate risk increase between the two warming scenarios was found for wheat (40%), followed by maize (35%) and soybean (23%). Looking at the impacts on agricultural production, we show that limiting global warming to 1.5 °C would avoid production losses of up to 2753 million (161,000, 265,000) tonnes maize (wheat, soybean) in the global breadbaskets and would reduce the risk of simultaneous crop failure by 26%, 28% and 19% respectively.

Abstract

Global warming is rapidly shifting climate conditions away from what societies and ecosystems are adapted to. While the magnitude of changes in mean and extreme climate are broadly studied, regional rates of change, a key driver of climate risk, have received less attention. Here we show, using large ensembles of climate model simulations, that large parts of the tropics and subtropics, encompassing 70% of current global population, are expected to experience strong (>2 s.d.) joint rates of change in temperature and precipitation extremes combined over the next 20 years, under a high-emissions scenario, dropping to 20% under strong emissions mitigation. This is dominated by temperature extremes, with most of the world experiencing unusual (>1 s.d.) rates relative to the pre-industrial period, but unusual changes also occur for precipitation extremes in northern high latitudes, southern and eastern Asia and equatorial Africa. However, internal variability is high for 20 year trends, meaning that in the near term, trends of the opposite sign are still likely for precipitation extremes, and rare but not impossible for temperature extremes. We also find that rapid clean-up of aerosol emissions, mostly over Asia, leads to accelerated co-located increases in warm extremes and influences the Asian summer monsoons.

Abstract

The Antarctic seasonal sea-ice zone (SIZ) is one of the most extensive and dynamic habitats on Earth. In summer, increased insolation and ice melt cause primary production to peak, sustaining large populations of locally-breeding seabirds. Due to their hypermobility, large Procellariiformes, including albatrosses, breeding in the subantarctic also have the potential to access the SIZ and track macroscale resource waves over the Sothern Ocean but the extent to which they do this is poorly known. Here, we analysed the foraging movements of breeding albatrosses and large petrels (seven species, 1298 individuals) recorded using GPS loggers and satellite-transmitters to quantify their use of sea-ice habitats and test whether they tracked seasonal drivers of primary production. Foraging latitudes of white-chinned petrels Procellaria aequinoctialis and black-browed Thalassarche melanophris, grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans varied sinusoidally over the breeding season, presumably in response to lagged effects of solar irradiance on primary production. Foraging latitudes of northern and southern giant petrels (Macronectes halli and M. giganteus), and light-mantled albatrosses Phoebetria palpebrata, exhibited no strong seasonal trend, but the latter two species spent ≥ 20 % of their time in the SIZ during incubation and post-brood, prior to or at the time of the spring ice breakup. Southern giant petrels travelled hundreds of km into the pack ice, encountering sea-ice concentrations up to 100 %, whereas light-mantled albatrosses remained almost exclusively in open water near the Marginal Ice Zone (MIZ). The remaining species spent up to 15 % of their time in the SIZ, typically from 5-7 weeks after breakup, and avoided the MIZ. This supports hypotheses that sea ice presents albatrosses but not giant petrels with physical barriers to flight or foraging, and that open-water-affiliated species use the SIZ only after primary production stimulated by ice melt transfers to intermediate trophic levels. Given that all seven species used the SIZ, it is likely that the phenology and demography of these and many other subantarctic-breeding seabirds are mechanistically linked to sea-ice dynamics. Declines in Antarctic sea ice predicted under climate change could therefore modulate and exacerbate the already unsustainable anthropogenic impacts being experienced by these populations.