PART 10/ Opdaterede Sol/Is/temp/hav data

Jørgen Petersen skrev:
Små vandhuller som f.eks. Middelhavet, Sortehavet og Østersøen opvarmes og afkøles altid hurtigere end de store oceaner. Det er der ikke noget nyt i. Der er bare ikke ret meget vand i disse vandhuller sammenlignet med de store oceaner.

Globally averaged projected surface warming ranges from about 1 °C for RCP2.6 to more than 3 °C for RCP8.5 during the 21st century, and at a depth of 1 000 m ranges from 0.5 °C for RCP2.6 to 1.5 °C for RCP8.5 [vi].

Tværtimod.

hvad skal man sige!!

delphi skrev:
I store træk det klimaforskningen gør er ændre talmaterialet repræsenterende fortiden så den interpolering af fremtiden hændelse man så fortager, kommer til at vise den runaway hændelse man ønsker.

delphi skrev:
Meget underholdende læsning se https://www.sciencedirect.com/science/article/pii/S0078323414500243 uden nogen som helst videnskabelig substans overhovedet. En masse henvisninger og luftige konklusioner ikke andet.

Havniveaustigninger, Bangladesh.

delphi skrev:
Meget underholdende læsning se

delphi skrev:
Men den samlede 'opgørelse' er langt i varmens favør når langt mindre dør af kulde, som er meget glædeligt.

uden nogen som helst videnskabelig substans overhovedet. Luftige konklusioner, ingen henvisninger, ikke andet.

Yet as the planet warms, some have been tempted to claim that cold-related deaths will decline overall. That's the argument Bjørn Lomborg, who has questioned many of the risks of climate change, made in the Wall Street Journal in 2016. He wrote that warming temperatures will "reduce the number of cold days and cold spells. That will cut the total number of cold-related deaths."

It sounds plausible. However, it's surprisingly difficult to figure out which is worse for public health as the climate becomes more unstable: the cold or the heat?

"That's a very controversial issue, actually," said Patrick Kinney, a professor of public health at Boston University. "As scientists, we haven't come to an agreement, especially about the future impacts of climate change."

delphi skrev:
https://www.britannica.com/science/medieval-warm-period varme perioder har til alle tider affødt velstand !!

Netop den periode er jo ikke et bevis for at varme er godt, kulde er skidt.
Vi ved ganske enkelt ikke nok om klimaet i middelalderen.

Jørgen Petersen skrev:
Følgende figur viser hvor man dyrker hvede i dag i Nordamerika, og hvor man regner med at kunne dyrke hvede i år 2050 i Nordamerika. Som det ses, så regner man med at kunne dyrke hvede langt længere imod nord i år 2050 en man kan i dag.

Jørgen Petersen skrev:
At stille spørgsmål ved om det nu også kan passe, at varme generelt er godt og kulde skidt, er som at stille spørgsmål ved, om det nu også er rigtigt, at en elefant er større end en mus.

For Canada, most analysts and farmers believe the potential rewards of climate change will outweigh the risks - at least over the next 30 years.

But if heat keeps on rising and causes greater water shortages and crop failures, Canada could see a decrease in farm productivity by the end of the century, said agriculture official Jarvis.

For now, improvements in farm technology, drought-resistant crops and new harvesting methods mean farmers should be poised to ramp up production as temperatures warm.

"Canada could be playing a bigger role providing the food for the world as heat rises," Jarvis said.

"Other countries are going to be affected (by climate change) much worse than we are," he said. "It's not a really happy picture overall."

We found that climate change has affected yields in many places. Not all of the changes are negative: Some crop yields have increased in some locations. Overall, however, climate change is reducing global production of staples such as rice and wheat. And when we translated crop yields into consumable calories – the actual food on people's plates – we found that climate change is already shrinking food supplies, particularly in food-insecure developing countries.

Wheat, rice, maize, and soybean provide two-thirds of human caloric intake. Assessing the impact of global temperature increase on production of these crops is therefore critical to maintaining global food supply, but different studies have yielded different results. Here, we investigated the impacts of temperature on yields of the four crops by compiling extensive published results from four analytical methods: global grid-based and local point-based models, statistical regressions, and field-warming experiments. Results from the different methods consistently showed negative temperature impacts on crop yield at the global scale, generally underpinned by similar impacts at country and site scales. Without CO2 fertilization, effective adaptation, and genetic improvement, each degree-Celsius increase in global mean temperature would, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%. Results are highly heterogeneous across crops and geographical areas, with some positive impact estimates. Multimethod analyses improved the confidence in assessments of future climate impacts on global major crops and suggest crop- and region-specific adaptation strategies to ensure food security for an increasing world population.

For every degree Celsius that the Earth warms, corn yields will go down an average of 7.4 percent, according to the study, which focused on the effects of rising temperatures and did not directly examine other influences related to climate change.

Agriculture as it exists today has been shaped by a climate system that has changed little over farming's 11,000-year history. Crops were developed to maximize yields in this long-standing climatic regime. As the temperature rises, agriculture will be increasingly out of sync with its natural environment. Nowhere is this more evident than in the relationship between temperature and crop yields.

Since crops in many countries are grown at or near their thermal optimum, even a relatively minor increase during the growing season of 1 or 2 degrees Celsius can shrink the grain harvest in major food-producing regions, such as the North China Plain, the Gangetic Plain of India, and the U.S. Corn Belt. 16

Higher temperatures can reduce or even halt photosynthesis, prevent pollination, and lead to crop dehydration. Although the elevated concentrations of atmospheric CO2 that raise temperature can also raise crop yields, the detrimental effect of higher temperatures on yields overrides the CO2 fertilization effect for the major crops.

In a study of local ecosystem sustainability, Mohan Wali and his colleagues at Ohio State University noted that as temperature rises, photosynthetic activity in plants increases until the temperature reaches 20 degrees Celsius (68 degrees Fahrenheit). The rate of photosynthesis then plateaus until the temperature hits 35 degrees Celsius (95 degrees Fahrenheit), whereupon it begins to decline, until at 40 degrees Celsius (104 degrees Fahrenheit), photosynthesis ceases entirely. 17

Climate change will affect agriculture, but unfortunately predicting how is not simple. Zhao et al. combined four analytical methods to predict the impact of global temperature increases on the yields of four crops. The results consistently indicate that rising temperatures will lead to reductions in crop yields. An increase of 1°C would be more severe for global maize yield (7.4% decrease) than for rice (3.2% decrease), and decreases in maize yield in the United States would be twice those seen in India (10.3 and 5.2%, respectively). Although this work points to worrying consequences of a warming world, it remains very difficult to predict the cumulative impact of multiple factors related to climate change, such as elevated atmospheric carbon dioxide concentrations and precipitation.