Allgemein

Jul

2022

Spain and Portugal suffering driest climate for 1,200 years, research shows

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 UK and Scandinavia more likely.

The scientists said the more frequent large Azores highs could only have been caused by the climate crisis, caused by humanity’s carbon emissions.

“The number of extremely large Azores highs in the last 100 years is really unprecedented when you look at the previous 1,000 years,” said Dr Caroline Ummenhofer, at Woods Hole Oceanographic Institution in the US

“[Our findings] have big implications for the water resources that are available for agriculture and other water intensive industries or for tourism,” said Ummenhofer. “It doesn’t bode well.”

Research in 2021 also linked the Azores high to the summer monsoon in India.

Jul

2022

Nonlocal effects dominate the global mean surface temperature response to the biogeophysical effects of deforestation

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 is deforested and at which latitude the deforestation takes place.

Jul

2022

The Food System’s Carbon Footprint Has Been Vastly Underestimated

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 IPCC guidelines, are breaking up the components of the food emissions, separating them, and burying them in [other] categories.”

The new analysis accounts for those emissions that the IPCC allocates to non-agricultural categories, including carbon dioxide from pre-production, like manufacturing fertilizer and farm equipment, and post-production emissions, such as food waste disposal, refrigeration, packaging, and transportation. It also includes as food-related emissions the conversion of natural ecosystems to agricultural land, which at nearly 3 billion metrics tons per year are the largest single source of greenhouse gas emissions in their analysis.

Source: CivilEats

Jul

2022

Securing the climate benefits of stable forests

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 intended to secure the climate-related benefits of stable forests have competed poorly against more urgent threats. Policymakers and finance mechanisms should view stable forests as a complementary element within a holistic, long-term approach to resource management.
International mechanisms and national frameworks should be adjusted and resourced to promote the long-term sustainability and permanence of stable forests.
Beyond additional resources, the climate benefits of stable forests may be best secured by pro-actively designing implementing policies that recognize the rights and interests of stakeholders who are affected by land management decisions.

Jul

2022

Analyzing precipitationsheds to understand the vulnerability of rainfall dependent regions

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 rainfed agricultural regions could be very sensitive to distant land cover changes.

Jul

2022

Sub-canopy microclimate temperatures of European forests

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 ± 1.6°C) lower in summer and 2.0°C higher (±0.7°C) in winter across Europe.

Jul

2022

Differences in temperature on open and vegetated soils (II)

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.

Jul

2022

The hidden crisis beneath our feet

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.

Jun

2022

Forests buffer against variations in precipitation

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 of monthly precipitation was 69% higher in areas where 50% of precipitation originates from non-forest land sources in the precipitationshed. Our results emphasize the importance of land cover composition in the precipitationshed to buffer precipitation variability downwind, in particular forest cover.

Jun

2022

Revealing the widespread potential of forests to increase low level cloud cover

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 67% of sampled areas across the world, afforestation would increase low level cloud cover, which should have a cooling effect on the planet. We further reveal a dependency of this effect on forest type, notably in Europe where needleleaf forests generate more clouds than broadleaf forests.

Jun

2022

Presentation: Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes

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 & co, more … and v. especially a cooling (of the layers near the ground), heat loss into space, more clouds with more precipitation and more sunlight reflection, which in turn contributes to the cooling of the climate, as well as activates the small (weakened) water cycles.

In short, we can(t) work with nature to cool the climate, strengthen the small water cycles, and in the process make agriculture, forestry, and water management more resilient and “fertile.”

This talk is based on the findings of my UNEP article (exists in French, Spanish, Chinese too).

Jun

2022

Cloud cooling effects of afforestation and reforestation at midlatitudes

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 temperate regions than previously considered.

Jun

2022

Article: Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes

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, increases in regional temperatures and an exacerbation of climate change. These changes affect regional climate, but can also impact regions far away. Understanding the interwoven relationships and the subsequent fluxes of energy between plants, soils and water on the ground, as well as in the atmosphere, can help mitigate climate change and create more resilient ecosystems.

Translations into French, Spanish, Chinese to be found here (#25).

Jun

2022

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks

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 that frequent extreme drought events have the potential to destabilize large parts of the Amazon forest.

Jun

2022

Differences in temperature on open and vegetated soils

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 good for the climate, because of warming of air temperature in this area, increased heat radiation, on larger areas potential development of high pressure areas, possible reduction of precipitation, … For more see my UNEP article and presentation, and the Climate Landscapes conference.

Jun

2022

The impact of global land-cover change on the terrestrial water cycle

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 drivers, affirming the important role of land-cover change in the Earth System.

Jun

2022

Human modification of global water vapor flows from the land surface

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 different, leading to major regional transformations of vapor-flow patterns. We analyze these changes in the light of future landuse-change projections that suggest widespread deforestation in sub-Saharan Africa and intensification of agricultural production in the Asian monsoon region. Furthermore, significant modification of vapor flows in the lands around the Indian Ocean basin will increase the risk for changes in the behavior of the Asian monsoon system.

Jun

2022

A planetary boundary for green water

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 variability for any month of the year. Provisional estimates […] indicate that the green water planetary boundary is already transgressed.

Jun

2022

Summer soil drying exacerbated by earlier spring greening of northern vegetation

Interesting article:

Earlier vegetation greening under climate change raises evapotranspiration and thus lowers spring soil moisture. […] We provide observational evidence that increased foliage cover over the Northern Hemisphere, during 1982–2011, triggers an additional soil moisture deficit that is further carried over into summer. […] attribute the driving process to be larger increases in evapotranspiration than in precipitation. This extra soil drying is projected to amplify the frequency and intensity of summer heatwaves. Most feedbacks operate locally, except for a notable teleconnection where extra moisture transpired over Europe is transported to central Siberia. Model results illustrate that this teleconnection offsets Siberian soil moisture losses from local spring greening.