The impact of diurnal variations of air traffic on contrail radiative forcing

We combined high resolution aircraft flight data from the EU Fifth Framework Programme project AERO2k with analysis data from the ECMWF's integrated forecast system to calculate diurnally resolved 3-D contrail cover. We scaled the contrail cover in order to match observational data for the Bakan area (eastern-Atlantic/western-Europe). <br><br> We found that less than 40% of the global distance travelled by aircraft is due to flights during local night time. Yet, due to the cancellation of shortwave and longwave effects during daytime, night time flights contribute a disproportional 60% to the global annual mean forcing. Under clear sky conditions the night flights contribute even more disproportionally at 76%. There are pronounced regional variations in night flying and the associated radiative forcing. Over parts of the North Atlantic flight corridor 75% of air traffic and 84% of the forcing occurs during local night, whereas only 35% of flights are during local night in South-East Asia, yet these contribute 68% of the radiative forcing. In general, regions with a significant local contrail radiative forcing are also regions for which night time flights amount to less than half of the daily total of flights. Therefore, neglecting diurnal variations in air traffic/contrail cover by assuming a diurnal mean contrail cover can over-estimate the global mean radiative forcing by up to 30%

Estimated human-induced warming from a linear temperature and atmospheric CO₂ relationship

Assessing compliance with the human-induced warming goal in the Paris Agreement requires transparent, robust and timely metrics. Linearity between increases in atmospheric CO₂ and temperature offers a framework that appears to satisfy these criteria, producing human-induced warming estimates that are at least 30% more certain than alternative methods. Here, for 2023, we estimate humans have caused a global increase of 1.49 ± 0.11 °C relative to a pre-1700 baseline

Understanding pattern scaling errors across a range of emissions pathways

The regional climate impacts of hypothetical future emissions scenarios can be estimated by combining Earth system model simulations with a linear pattern scaling model such as MESMER (Modular Earth System Model Emulator with spatially Resolved output), which uses estimated patterns of the local response per degree of global temperature change. Here we use the mean trend component of MESMER to emulate the regional pattern of the surface temperature response based on historical single-forcer and future Shared Socioeconomic Pathway (SSP) CMIP6 (Coupled Model Intercomparison Project Phase 6) simulations. Errors in the emulations for selected target scenarios (SSP1–1.9, SSP1–2.6, SSP2–4.5, SSP3–7.0, and SSP5–8.5) are decomposed into two components, namely (1) the differences in scaling patterns between scenarios as a consequence of varying combinations of external forcings and (2) the intrinsic time series differences between the local and global responses in the target scenario. The time series error is relatively small for high-emissions scenarios, contributing around 20 % of the total error, but is similar in magnitude to the pattern error for lower-emissions scenarios. This irreducible time series error limits the efficacy of linear pattern scaling for emulating strong mitigation pathways and reduces the dependence on the predictor pattern used. The results help guide the choice of predictor scenarios for simple climate models and where to target for the introduction of other dependent variables beyond global surface temperature into pattern scaling models

Observed trend in Earth energy imbalance may provide a constraint for low climate sensitivity models

Climate forcings by greenhouse gases and aerosols cause an imbalance at the top of the atmosphere between the net incoming solar radiation and outgoing longwave radiation from Earth. This Earth energy imbalance has strengthened over the period 2001 to 2023 with satellite data. Here, we show that low climate sensitivity models fail to reproduce the trend in Earth energy imbalance, particularly in the individual longwave and shortwave contributions to the imbalance trend. The inability to produce a strong positive shortwave and strong negative longwave Earth energy imbalance trend is found to be a robust feature in the low climate sensitivity models, especially for models with a climate sensitivity below 2.5 kelvin. The negative longwave contribution to Earth energy imbalance is driven by surface temperature increases and is therefore most pronounced in high climate sensitivity models, whereas the shortwave contribution is generally positive and amplified by greater surface warming

Future forests: estimating biogenic emissions from net-zero aligned afforestation pathways in the UK

Woodlands sequester carbon dioxide from the atmosphere, which could help mitigate climate change. As part of efforts to reach net-zero greenhouse gas emissions by the year 2050, the UK's Climate Change Committee (CCC) recommend increasing woodland cover from a UK average of 13 % to 17 %–19 %. Woodlands can also have benefits for air quality. However, they emit biogenic volatile organic compounds (BVOCs) which are precursors to atmospheric pollutants, such as ozone (O3) and particulate matter (PM), which have the potential to degrade air quality. Here we make an estimate of the potential impact of afforestation in the UK on BVOC emissions, coupling information on tree species' emissions potential, planting suitability and policy-informed land cover change. We quantify the potential emission of BVOCs from five afforestation experiments using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) (v2.1) in the Community Land Model (CLM) (v4.5) for the year 2050. Experiments were designed to explore the impact of variation in BVOC emissions potentials between and within plant functional types (PFTs) on estimates of BVOC emissions from UK land cover, in a future warmer climate under elevated atmospheric CO2 concentrations, to understand the scale of change associated with afforestation to 19 % woodland cover by the year 2050. Our estimate of current annual UK emissions is 39 kt yr−1 for isoprene and 46 kt yr−1 for total monoterpenes. Broadleaf afforestation results in a change to UK isoprene emission of between −3 % and +123 %, and a change to total monoterpene emission of between +5 % and +48 %. Needleleaf afforestation leads to a change in UK isoprene emission of between −3 % and +22 %, and a change to total monoterpene emission of between +60 % and +86 %. Our study highlights the potential for net-zero aligned afforestation, in a likely warmer and drier future UK climate, to have substantial impacts on BVOC emissions. However, the results highlight possible pathways to achieving 19 % woodland cover without requiring large increases in isoprene emissions. The emissions estimates presented here provide the opportunity to quantify future impacts on air pollution associated with changes in biogenic emissions, as well as how these impacts would be affected by concurrent changes in anthropogenic emissions

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

Modifying emissions scenario projections to account for the effects of COVID-19: protocol for CovidMIP

Lockdowns to avoid the spread of COVID-19 have created an unprecedented reduction in human emissions. While the country-level scale of emissions changes can be estimated in near real time, the more detailed, gridded emissions estimates that are required to run general circulation models (GCMs) of the climate will take longer to collect. In this paper we use recorded and projected country-and-sector activity levels to modify gridded predictions from the MESSAGE-GLOBIOM SSP2-4.5 scenario. We provide updated projections for concentrations of greenhouse gases, emissions fields for aerosols, and precursors and the ozone and optical properties that result from this. The code base to perform similar modifications to other scenarios is also provided. We outline the means by which these results may be used in a model intercomparison project (CovidMIP) to investigate the impact of national lockdown measures on climate, including regional temperature, precipitation, and circulation changes. This includes three strands: an assessment of short-term effects (5-year period) and of longer-term effects (30 years) and an investigation into the separate effects of changes in emissions of greenhouse gases and aerosols. This last strand supports the possible attribution of observed changes in the climate system; hence these simulations will also form part of the Detection and Attribution Model Intercomparison Project (DAMIP)

Preserving Madagascar’s Natural Heritage: The Importance of Keeping the Islands’s Fossils in the Public Domain

Article argues for the development of adequate repositories and support infrastructure in Madagascar to safeguard and display the country’s vertebrate fossil collections; doing so would ensure the preservation and appreciation of Madagascar’s rich natural heritage for future generations of scientists and Malagasy citizens alike

Spatial variations in lead isotopes, Tasman Element, eastern Australia

Lead isotope data from ore deposits and mineral occurrences in the Tasman Element of eastern Australia have been used to construct isotopic maps of this region. These maps exhibit systematic patterns in parameters derived from isotope ratios. The parameters include μ (238U/204Pb), as calculated using the Cumming and Richards (1975) lead evolution model, and the difference between true age of mineralisation and the Cumming and Richards lead isotope model age of mineralisation (Δt). Variations in μ coincide with boundaries at the orogen, subprovince and zone scales. The boundary between the Lachlan and New England orogens is accompanied by a decrease in μ, and within the Lachlan Orogen, the Central Subprovince is characterised by μ that is significantly higher than in the adjacent Eastern and Western subprovinces. Within the Eastern Subprovince, the Cu-Au-rich Macquarie Arc is characterised by significantly lower μ relative to adjacent rocks. The Macquarie Arc is also characterised by very high Δt (generally above 200 Myr). Other regions characterised by very high Δt include western Tasmania, the southeastern New England Orogen, and the Hodgkinson Province in northern Queensland. These anomalies are within a broad pattern of decreasing Δt from east to west, with Paleozoic deposits within or adjacent to Proterozoic crust characterised by Δt values of 50 Myr or below. The patterns in Δt are interpreted to reflect the presence of the two major tectonic components involved in the Paleozoic Tasman margin in Australia (cf., Münker, 2000): subducting proto-Pacific crust (Δt >150 Myr), and Proterozoic Australia crust (Δt < 50 Myr) on the over-riding plate. Proterozoic Australia crustal sources are interpreted to dominate the western parts of the Tasman Element and Proterozoic crust further to the west, whereas Pacific crustal sources are inferred to characterise western Tasmania and much of the eastern part of the Tasman Element. Contrasts in Δt between the Cambrian Mount Read Volcanics in western Tasmania and similar aged rocks in western Victoria and New South Wales make direct tectonic correlation between these rocks problematic