Klimarealister: Myten om europæisk tørke II

Abstract
Vi analyserede langsigtede variationer og tendenser i meteorologiske tørke i hele Vesteuropa ved hjælp af Standardized Precipitation Index (SPI). Nedbørsdata fra 199 stationer, der spænder over perioden 1851–2018, blev efter homogenisering anvendt til at udlede SPI-3 og SPI-12-serier for hver station sammen med indeks for tørkevarighed og sværhedsgrad. Resultaterne afslører et generelt fravær af statistisk signifikante langsigtede tendenser i undersøgelsesdomænet med undtagelse af signifikante tendenser på nogle stationer, der generelt dækker korte perioder. De største faldende tendenser i SPI-3 (dvs. stigende tørkeforhold) blev fundet til sommer på de britiske og irske øer. Generelt har tørkeepisoder, der er oplevet i de sidste to eller tre årtier, præcedenser i de sidste 170 år og understreger vigtigheden af lange optegnelser for at vurdere forandringer. Hovedkarakteristikken ved tørkevariabilitet i Vesteuropa er dens stærke rumlige mangfoldighed, hvor regioner udviser en homogen tidsmæssig udvikling. Især er den tidsmæssige variation i tørke i Vesteuropa mere dominerende end langsigtede tendenser. Dette antyder, at langsigtede tørkeudviklinger ikke kan bekræftes i Vesteuropa ved hjælp af nedbørsposter alene. Denne undersøgelse giver en langsigtet regional vurdering af tørkevariabilitet i Vesteuropa, som kan bidrage til en bedre forståelse af regionale klimaændringer i de sidste to århundreder.

Key messages
Tørke er et tilbagevendende træk ved det europæiske klima, der påvirker betydelige dele af den europæiske befolkning hvert år.

Hyppigheden og sværhedsgraden af meteorologiske og hydrologiske tørke er steget i de fleste dele af Europa. Forskellige tørkeindeks er enige om, at stigningen er størst i Sydeuropa.

Tilgængelige undersøgelser projekterer yderligere stigninger i hyppigheden, varigheden og sværhedsgraden af meteorologiske og hydrologiske tørke i det meste af Europa i det 21. århundrede, bortset fra dele af det centraløstlige og nordøstlige Europa. Den største stigning i tørkeforhold forventes for Sydeuropa, hvor det vil øge konkurrencen mellem forskellige vandbrugere, såsom landbrug, industri, turisme og husholdninger.

Highlights

Drought seasonal trends have been investigated for the entire Europe.

The input data are temperature and precipitation from the E-OBS grids.

We computed two indicators, the SPI and the SPEI for the period 1950–2014.

Drought frequency and severity increased especially in the Southern and Eastern Europe in summer and autumn.

Drought frequency and severity decreased especially in Northern Europe in winter and spring.

Abstract
In the last decades drought has become one of the natural disasters with most relevant impacts in Europe and this not only in water scarce areas such as the Mediterranean that are inclined to such events. As a complex natural phenomenon, drought is characterized by many hydro-meteorological aspects, a large variety of possible impacts and definitions. This study focuses on meteorological drought, investigated by using indicators that include precipitation and potential evapotranspiration (PET), i.e. the Standardized Precipitation Index (SPI) and the Standardized Precipitation-Evapotranspiration Index (SPEI). These indicators account for the lack of precipitation and the drying effects of hot temperatures and in this study have been computed for short-accumulation periods (3-month) to capture the seasonality of droughts. The input variables, monthly precipitation and temperature for 1950–2015, stem from daily gridded E-OBS data and indicators were computed on regular grids spanning over the whole of Europe. PET was calculated from minimum and maximum temperatures using the Hargreaves-Samani formulation. Monthly precipitation and PET have then been used to compute the SPI-3 and the SPEI-3 time series. From these series drought events were defined at seasonal scale and trends of frequency and severity of droughts and extreme droughts were analyzed for the periods 1950–2015 and 1981–2015. According to the SPI (driven by precipitation), results show a statistically significant tendency towards less frequent and severe drought events over North-Eastern Europe, especially in winter and spring, and a moderate opposite tendency over Southern Europe, especially in spring and summer. According to the SPEI (driven by precipitation and temperature), Northern Europe shows similar wetting patterns, while Southern and Eastern Europe show a more remarkable drying tendency, especially in summer and autumn. Both for frequency and severity, the evolution towards drier conditions is more relevant in the last three decades over Central Europe in spring, the Mediterranean area in summer, and Eastern Europe in autumn.

GW medfører, at det samlede areal der er egnet til planteavl bliver forøget. Det tager disse analyser ikke hensyn til, og derfor giver de et misvisende resultat. Et resultat hvor der et åbent lyst misforhold imellem det vi kan læse i disse rapporter, og det vi rent faktuel kan konstatere

The largest corn harvest in history is among the reasons the International Grains Council (IGC) is forecasting record total grains production in 2020-21.

According to the IGC's Grain Market Review, released Aug. 27, total global grains production will reach 2.230 billion tonnes this marketing year, up 50 million tonnes from the July forecast and 9% higher than the previous year (2.181 billion tonnes)...

The fact remains that plant metabolisms are temperature sensitive. Key crops such as winter wheat, rice and maize photosynthesize best at temperatures between 25C and 30C. Daily temperatures exceeding this range are likely to slow crop production and damage both the quality and quantity of crop yields.

The consequences according to the report will be severe. Producers will be affected by increases in crop water requirements, the degradation of soil, intensive rainfall events and potential release of large-scale methane emission through thawing permafrost (ground, including rock or soil, at or below the freezing point of water 0 degrees C for two or more years).

Chronic high temperatures will add to the evaporative demand of crop systems. This will lead to a rise in the water requirement for crop growth. Thus, agricultural water-systems will be working at an increased rate, an astounding prospect given the industry today is already the single largest user of freshwater resources, using a global average of 70% of all surface water supplies. These factors will make agriculture in the future progressively more challenging.

Et nyt studie af satellitbilleder fra NASA viser, at jordens grønne områder er vokset med 5 % eller over 5 millioner kvadratkilometer siden årtusindeskiftet.

Det må da være svært at bevare pessimismen!!!

Plants have an engineering problem. The stomata, the minute openings on the underside of the leaf, take in CO2, but water evaporates from the plant at a higher rate when it does. With higher CO2 concentrations the stomata can contract, resulting in less water loss. This is particularly true for plants classified as C3, which include wheat, rice, rye, oats, peanuts, cassava, soybean, and most trees, including fruit trees