Megacities depend on downwind evapotranspiration: Our results reveal that 19 of 29 megacities depend for more than a third of their water supply on evaporation from land. We also show that for many of the megacities, the terrestrial dependence is higher in dry years. This high dependence on terrestrial evaporation for their precipitation exposes these cities to potential land-use change that could reduce the evaporation that generates precipitation. […] reveals four highly vulnerable megacities (Karachi,
Puhh…. Most rain on the Iberian peninsula falls in winter as wet, low-pressure systems blow in from the Atlantic. But a high-pressure system off the coast, called the Azores high, can block the wet weather fronts. The researchers found that winters featuring “extremely large” Azores highs have increased dramatically from one winter in 10 before 1850 to one in four since 1980. These extremes also push the wet weather northwards, making downpours in the northern
Nonlocal effects: Deforestation influences surface temperature at the location of deforestation (local effects) and elsewhere (nonlocal effects). […] Using simulations in a climate model, we show that deforestation-induced changes in the brightness of the surface influence surface temperature mainly nonlocally and thus may be largely overlooked in observation-based data sets. The simulations show that the nonlocal effects have a larger impact on global average surface temperature than the local effects, independent of how much area
Let it (possibly) rain: Some bacteria have the unique capacity of synthesising ice-nucleation-active (INA) proteins and exposing them at their outer membrane surface. […] During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry INA genes, were dominant. A screening for INA properties revealed that ~12% of the cultivable bacteria caused ice formation at ≤-7 °C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective
Scientists found in their study that the global food system was responsible for 16 billion metric tons of greenhouse gas emissions in 2018, or a third of all global emissions that year. This is a sharp contrast to the more narrowly defined agriculture sector of the IPCC’s categories for greenhouse gas inventories, which accounted for 5.3 billion metric tons in 2018, or just a tenth of the total. “The national greenhouse gas inventories, [under] the
Stable forests: We argue that resource and finance allocation for stable forests should be incorporated into countries’ and donors’ comprehensive portfolios aimed at tackling deforestation and forest degradation as well as resulting emissions. Key policy insights: Climate policies, finance, and implementation have tended to focus on areas of recent forest loss and near-term threats of anthropogenic disturbance, resulting in an imbalance of effort that fails to adequately address stable forests. In some contexts, policy measures
Concept of precipitationsheds, defined as the upwind atmosphere and surface that contributes evaporation to a specific location’s precipitation.: We illustrate the importance of upwind land cover in precipitationsheds to sustain precipitation in critically water stressed downwind areas, specifically dryland agricultural areas. […] This work demonstrates that seemingly separate parts of Earth’s biophysical system are interlinked with its social systems. Indeed, our results and analysis suggest that food security in some of the world’s most water-constrained
Mind the difference between air temperature measured in 2m height and at the ground: Ecological research heavily relies on coarse-gridded climate data based on standard- ized temperature measurements recorded at 2 m height in open landscapes. However, many organisms experience environmental conditions that differ substantially from those captured by these macroclimatic (i.e. free air) temperature grids. […]. We found that sub-canopy air tem- peratures differ substantially from free-air temperatures, being on average 2.1°C (standard deviation
Been out again yesterday, and made a few new measurements. Astonishing the high temperatures on the open ground with >50°C – as hot as the asphalt. And also fascinating the comparison between “on the mulch” and “under the mulch” for vegetables: 24°C difference.
Disappearing groundwater requires action to prevent widespread water scarcity Groundwater is the primary water source for billions of people and for nearly half of irrigated agriculture, yet its incon- spicuous presence has allowed groundwater to elude effective governance and manage- ment in countless regions around the world. Consequently, more than half of the world’s major aquifers are being depleted, some of them at an alarming pace.
More forest, more stable rains: We found a significant buffering effect of forests in the precipitation variability of 10 out of 14 biomes globally. On average, if 50% of precipitation originates from forest, then we find a reduction in the coefficient of variation of monthly precipitation of 60%. We also observed that a high fraction of precipitation from non-forest land sources tends to have the opposite effect, that is, no buffering effect. The average variation
Forests and their impacts on low level clouds: However, changing the forest cover can further affect the climate system through biophysical effects. One such effect that is seldom studied is how afforestation can alter the cloud regime, which can potentially have repercussions on the hydrological cycle, the surface radiation budget and on planetary albedo itself. Here we provide a global scale assessment of this effect derived from satellite remote sensing observations. We show that for
My presentation on “Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes“. As it looks, we have a pretty exciting tool in the climate as well as agriculture discussion with multiple benefits: more vegetation (especially in agriculture; through undersowing, intercropping, agroforestry, but also through a different form of animal husbandry, forest conversion, water retention) means more fertile soils, more water storage capacity and infiltration, more nutrients, more habitat for insects
Interesting analysis: Here, we carefully analyze the situation for reforestation and afforestation (R&A) at midlatitudes, where the warming effects due to vegetation albedo are regarded to be almost balanced by the cooling effects from an increased carbon storage. Using both satellite data and atmospheric boundary-layer models, we show that by including cloudalbedo effects due to land–atmosphere interactions, the R&A cooling at midlatitudes becomes prevalent. This points to a much greater potential of R&A for wet
My UNEP paper on “Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes“. The continued destruction of forests, the deterioration of soils, the subsequent loss of terrestrial soil water storage and the reduction of water retention in the landscape are disrupting the movement of water in and through the atmosphere. This disruption causes major shifts in precipitation that could lead to less rainfall and more droughts in many areas of the world,
Vicious cycle of destruction in the Amazon: Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. […] Our results suggest that the risk of self-amplified forest loss is reduced with increasing heterogeneity in the response of forest patches to reduced rainfall. […] Although our findings do not indicate that the projected rainfall changes for the end of the twenty-first century will lead to complete Amazon dieback, they suggest
Yesterday, at gentle 24 ° C air temperature, I measured the soil surface temperatures (for the first time). On the areas with open soil in the corn field of our neighbour: over 50°C. In the clover grass on our side: 26°C. It’s amazing how the soil heats up (and was another 6°C warmer than the (rough) road next to it). Problematic not only for the soil life, soil water and for many crops. Also not
Human induced changes on the terrestrial water cycle: Geographic modelling reveals that land-cover change reduces annual total evapotranspiration by approximately 3,500 km3/yr (5%) and that the largest changes in evapotranspiration are associated with wetlands and reservoirs. Land surface model simulations support these evapotranspiration changes, and project increased runoff (7.6%) as a result of land-cover changes. […] The results demonstrate that land-cover change alters annual global runoff to a similar or greater extent than other major
Deforestation and the global water cycle: We show that deforestation is as large a driving force as irrigation in terms of changes in the hydrological cycle. Deforestation has decreased global vapor flows from land by 4% (3,000 km3/yr), a decrease that is quantitatively as large as the increased vapor flow caused by irrigation (2,600 km3/yr). Although the net change in global vapor flows is close to zero, the spatial distributions of deforestation and irrigation are
Important paper: Green water — terrestrial precipitation, evaporation and soil moisture — is fundamental to Earth system dynamics and is now extensively perturbed by human pressures at continental to planetary scales. However, green water lacks explicit consideration in the existing planetary boundaries framework that demarcates a global safe operating space for humanity. The green water planetary boundary can be represented by the percentage of ice-free land area on which root-zone soil moisture deviates from Holocene
