Ten New Insights in Climate Science 2023/2024

Non-technical summary: We identify a set of essential recent advances in climate change research with high policy relevance, across natural and social sciences: (1) looming inevitability and implications of overshooting the 1.5°C warming limit, (2) urgent need for a rapid and managed fossil fuel phase-out, (3) challenges for scaling carbon dioxide removal, (4) uncertainties regarding the future contribution of natural carbon sinks, (5) intertwinedness of the crises of biodiversity loss and climate change, (6) compound events, (7) mountain glacier loss, (8) human immobility in the face of climate risks, (9) adaptation justice, and (10) just transitions in food systems. Technical summary The IPCC Assessment Reports offer the scientific foundation for international climate negotiations and constitute an unmatched resource for climate change researchers. However, the assessment cycles take multiple years. As a contribution to cross- and interdisciplinary understanding across diverse climate change research communities, we have streamlined an annual process to identify and synthesise essential research advances. We collected input from experts on different fields using an online questionnaire and prioritised a set of ten key research insights with high policy relevance. This year we focus on: (1) looming overshoot of the 1.5°C warming limit, (2) urgency of phasing-out fossil fuels, (3) challenges for scaling carbon dioxide removal, (4) uncertainties regarding the future of natural carbon sinks, (5) need for join governance of biodiversity loss and climate change, (6) advances in the science of compound events, (7) mountain glacier loss, (8) human immobility in the face of climate risks, (9) adaptation justice, and (10) just transitions in food systems. We first present a succinct account of these Insights, reflect on their policy implications, and offer an integrated set of policy relevant messages. This science synthesis and science communication effort is also the basis for a report targeted to policymakers as a contribution to elevate climate science every year, in time for the UNFCCC COP. Social media summary We highlight recent and policy-relevant advances in climate change research - with input from more than 200 experts 1. © 2023 Cambridge University Press. All rights reserved. There are 78 total authors to this piece. We have listed the first twelve. The available download is the accepted manuscript

Ten new insights in climate science 2022

Non-technical summary We summarize what we assess as the past year's most important findings within climate change research: limits to adaptation, vulnerability hotspots, new threats coming from the climate–health nexus, climate (im)mobility and security, sustainable practices for land use and finance, losses and damages, inclusive societal climate decisions and ways to overcome structural barriers to accelerate mitigation and limit global warming to below 2°C. Technical summary We synthesize 10 topics within climate research where there have been significant advances or emerging scientific consensus since January 2021. The selection of these insights was based on input from an international open call with broad disciplinary scope. Findings concern: (1) new aspects of soft and hard limits to adaptation; (2) the emergence of regional vulnerability hotspots from climate impacts and human vulnerability; (3) new threats on the climate–health horizon – some involving plants and animals; (4) climate (im)mobility and the need for anticipatory action; (5) security and climate; (6) sustainable land management as a prerequisite to land-based solutions; (7) sustainable finance practices in the private sector and the need for political guidance; (8) the urgent planetary imperative for addressing losses and damages; (9) inclusive societal choices for climate-resilient development and (10) how to overcome barriers to accelerate mitigation and limit global warming to below 2°C. Social media summary Science has evidence on barriers to mitigation and how to overcome them to avoid limits to adaptation across multiple fields

Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those ‘next users’ of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem\u27s carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers

Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those ‘next users’ of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.</p

Ten new insights in climate science 2020 – a horizon scan

Non-technical summary We summarize some of the past year's most important findings within climate change-related research. New research has improved our understanding of Earth's sensitivity to carbon dioxide, finds that permafrost thaw could release more carbon emissions than expected and that the uptake of carbon in tropical ecosystems is weakening. Adverse impacts on human society include increasing water shortages and impacts on mental health. Options for solutions emerge from rethinking economic models, rights-based litigation, strengthened governance systems and a new social contract. The disruption caused by COVID-19 could be seized as an opportunity for positive change, directing economic stimulus towards sustainable investments. Technical summary A synthesis is made of ten fields within climate science where there have been significant advances since mid-2019, through an expert elicitation process with broad disciplinary scope. Findings include: (1) a better understanding of equilibrium climate sensitivity; (2) abrupt thaw as an accelerator of carbon release from permafrost; (3) changes to global and regional land carbon sinks; (4) impacts of climate change on water crises, including equity perspectives; (5) adverse effects on mental health from climate change; (6) immediate effects on climate of the COVID-19 pandemic and requirements for recovery packages to deliver on the Paris Agreement; (7) suggested long-term changes to governance and a social contract to address climate change, learning from the current pandemic, (8) updated positive cost–benefit ratio and new perspectives on the potential for green growth in the short- and long-term perspective; (9) urban electrification as a strategy to move towards low-carbon energy systems and (10) rights-based litigation as an increasingly important method to address climate change, with recent clarifications on the legal standing and representation of future generations. Social media summary Stronger permafrost thaw, COVID-19 effects and growing mental health impacts among highlights of latest climate science

Dynamics of carbon exchange in a <I>Eucalyptus</I> forest in response to interacting disturbance factors

Carbon (C) sinks created by forests depend on the balance between C uptake through photosynthesis and loss through respiration. This balance varies depending on the relative effect of environmental drivers on these processes. Components and dynamics of the C cycle were measured in a native Eucalyptus delegatensis forest at Tumbarumba in south-eastern Australia during conditions of average rainfall (1998-2001) and droughts (2002-2003 and 2006-2007). In 2002-03 there were interacting disturbance factors of dry conditions and insect damage that reduced the photosynthetically active leaf area in the canopy. Conditions during the droughts included reduced soil moisture content, higher temperatures and increased vapour pressure deficit. Similarly low soil moisture contents occurred during both drought periods, but lasted for longer in 2002-03. The combined impact of drought stress and insect damage resulted in markedly reduced growth (45-80%) and higher mortality of trees (5-60%). Impacts were variable across the 50,000ha of forest, with mortality greatest in stands with normally highest growth rates, and in locations with greatest reductions in soil moisture. Growth rates were reduced during 2002-03, most severely in 2003-04, and recovering in 2004-05. Mortality remained high in 2004-05 indicating the prolonged effect of the stress conditions. The total C pool in the forest is 483tCha -1 with net C uptake of -6.7tCha -1yr -1 in the growing season prior to the insect attack (2001-02). Under conditions of drought and insect disturbance in 2003 the forest released a total of 1.7tCha -1 over 8 months, while under conditions of drought alone carbon uptake was -6.5tCha -1yr -1 in the growing season year of 2006-07 and -5.6tCha -1yr -1 in the calendar year of 2007. Interacting stress factors of drought and insect damage resulted in a large imbalance in the C budget with a 26% reduction in gross primary productivity and a 9% reduction in ecosystem respiration, whereas drought alone had a much lesser effect. Drought conditions result in (1) weather conditions that break the synchronisation of insects with parasites and predators resulting in insect outbreaks, (2) moisture stress that predisposes trees to attack by insects, and (3) moisture stress that restricts leaf regeneration after damage. Climate change and climatically induced changes in disturbance regimes may affect the processes of photosynthesis and respiration differently and hence change the balance of net ecosystem C exchange. Reduced sink strength of forests will lead to positive C cycle-climate feedbacks, which enhance the greenhouse effect and climate change

Regional evaporation estimates from flux tower and MODIS satellite data

Two models were evaluated for their ability to estimate land surface evaporation at 16-day intervals using MODIS remote sensing data and surface meteorology as inputs. The first was the aerodynamic resistance–surface energy balance model, and the second was the Penman–Monteith (P–M) equation, where the required surface conductance is estimated from remotely-sensed leaf area index. The models were tested using 3 years of evaporation and meteorological measurements from two contrasting Australian ecosystems, a cool temperate, evergreen Eucalyptus forest and a wet/dry, tropical savanna. The aerodynamic resistance–surface energy balance approach failed because small errors in the radiative surface temperature translate into large errors in sensible heat, and hence into estimates of evaporation. The P–M model adequately estimated the magnitude and seasonal variation in evaporation in both ecosystems (RMSE = 27 W m− 2, R2 = 0.74), demonstrating the validity of the proposed surface conductance algorithm. This, and the ability to constrain evaporation estimates via the energy balance, demonstrates the superiority of the P–M equation over the surface temperature-based model. There was no degradation in the performance of the P–M model when gridded meteorological data at coarser spatial (0.05°) and temporal (daily) resolution were substituted for locally-measured inputs. The P–M approach was used to generate a monthly evaporation climatology for Australia from 2001 to 2004 to demonstrate the potential of this approach for monitoring land surface evaporation and constructing monthly water budgets from 1-km to continental spatial scales

Linking Urbanization and the Environment: Conceptual and Empirical Advances

Urbanization is one of the biggest social transformations of modern time, driving and driven by multiple social, economic, and environmental processes. The impacts of urbanization on the environment are profound, multifaceted and are manifested at the local, regional, and global scale. This article reviews recent advances in conceptual and empirical knowledge linking urbanization and the environment, focusing on six core aspects: air pollution, ecosystems, land use, biogeochemical cycles and water pollution, solid waste management, and the climate. We identify several emerging trends and remaining questions in urban environmental research, including (a) increasing evidence on the amplified or accelerated environmental impacts of urbanization; (b) varying distribution patterns of impacts along geographical and other socio-economic gradients; (c) shifting focus from understanding and quantifying the impacts of urbanization toward understanding the processes and underlying mechanisms; (d) increasing focus on understanding complex interactions and interlinkages among different environmental, social, economic, and cultural processes; and (e) conceptual advances that call for articulating and using a systems approach in cities. In terms of governing the urban environment, there is an increasing focus on public participation and coproduction of knowledge with stakeholders. Cities are actively experimenting toward sustainability under a plethora of guiding concepts that manifests their aspirational goals, with varying levels of implementation and effectiveness.T.M.’s participation was supported by the Urban Resilience to Extreme Weather-Related Events Sustainability Research Network (URExSRN; NSF grant no. SES 1444755)

Application of an alternative method to derive reliable estimates of nighttime respiration from eddy covariance measurements in moderately complex topography

Even moderately complex topography can lead to significant horizontal and vertical advection and a consequent underestimation of nocturnal CO2 effluxes derived from eddy covariance measurements on a single tower. The standard approach to select nighttim