UN?s Climate Convention (UNFCCC) agreed in November 2015 to try to limit the global warming to 1.5 degrees C above pre-industrial levels, even if there were little scientific knowledge about the differences in climate and its consequences between 1.5 og 2 degrees global warming, or the feasibility and requirements of keeping the warming below 1.5 degrees. UN?s Intergovernmental Panel on Climate Change (IPCC) decided shortly after the meeting to produce a Special Report (SR) on these subjects, and the report was released on October 8. 2018.
In order to contribute to IPCC?s Special Report, the HappiEVA project has carried out a large number of calculations of the global climate as of today (2006-15; PD), which is estimated to be approx. 0.8 degrees C above the pre-industrial level in 1850, and for the two future levels of global warming addressed by the IPCC SR: 1.5 and 2 degrees C above the 1850 level.
The calculations follow an experiment protocol in the international cooperation project HAPPI (www.happimip.org). HAPPI has collected a large number of commonly designed calculations from different climate models, with the purpose of calculating the climate in its full range for the three mentioned levels of the global temperature (PD, 1.5 and 2). The data makes it possible to calculate both a wide range of natural climate variations and to estimate uncertainties due to model weaknesses. Furthermore, the large number of calculations for each state (926) enables estimates of the difference in natural appearance of extremely rare events between the three states (PD, 1.5 and 2).
A number of publications were written on the basis of the data, and researchers in HappiEVA analyzed results for several of them. The greatest emphasis was placed on the differences between the 1.5 and 2 degree targets for global temperature increase. One of the papers had lead authors from HappiEVA. The analyses in that work show, among other things, that we get more cyclones over eastern parts of the North Atlantic and in Northwest Europe. This means that considerably more precipitation is calculated over Northern Europe. Over the Mediterranean, fewer cyclones and less rainfall are calculated, and the rainfall reduction in winter is much stronger at 2 degrees of global warming than at 1.5 degrees.
The water supply in the Mediterranean region is dependent on enough winter rainfall, hence both natural and social consequences can be significant. HappiEVA researchers have contributed to several articles that address the effects that the increased frequency of drought has on people and different societies. The analyses are based on selected extreme weather indices and show that a wide range of aspects of climate change affecting people and society, can be quantified. One of the studies shows a 20 percent increase in mortality in humans related to heat when global warming increases from 1.5 to 2 degrees. Another study shows that the difference between rich and poor countries is further aggravated by a corresponding change in temperature. A third study looks at how temperature and precipitation extremes at the two targets for global temperature rise affect and are influenced by changes in land use. Again, the results show considerable differences between 1.5 and 2 degrees of global warming.
An article, which is still under evaluation for publication, documents the Norwegian model system used in the project. The model is also used to investigate the importance of processes in the oceans and the sea-ice in the Arctic. The main conclusion is that ocean and sea-ice contribute to considerably strengthen the Arctic temperature signal. As a result, reduced differences in temperature are calculated near the ground between the tropics and the Arctic by global warming. Furthermore, it is calculated that ice-free Arctic conditions can become 5-6 times more frequent at 2 degrees global warming than at 1.5 degrees. The studies in HappiEVA indicate that there are both scientific and ethical reasons for striving to limit the global temperature rise to 1.5 degrees above pre-industrial conditions.
The COP of UNFCCC, in its Paris Agreement of 2015, invited the Intergovernmental Panel on Climate Change (IPCC) to prepare a Special Report in 2018 on the impacts of global warming of 1.5C above pre-industrial levels and related greenhouse gas emission pathways. To inform such an assessment, research will need to be undertaken immediately, over the period 2016 to 2017. The international project HAPPI (http://www.happimip.org) lead by Dr D. Mitchell at Univ. of Bristol is an important channel for contributions from global climate models.
Due to the ongoing activities in the RCN-financed project EVA, we are able to take on the ad hoc tasks in HappiEVA. With extraordinary access to High Performance Computer (HPC) resources provided by the Bjerknes Centre at University of Bergen, existing well suited software, and the dedication of highly qualified personnel, it is possible to contribute on a very short notice based on the Norwegian Earth System Model (NorESM) with one degree resolution.
Contributions will also include analyses of the common set of multimodel data in HAPPI, and further investigations of the importance of Arctic amplification. Significant contributions to planned scientific papers will be made, in due time for inclusion in the scheduled IPCC Special Report.
A major outcome of the project is the NorESM1_Happi model runs for present-day climate, and for a low (1.5C above 1850) and a high ceiling (2C above 1850) of the global temperature change. These model-generated data were scheduled to be provided to HAPPI in the autumn 2016, but were delayed due to delayed input data from HAPPI.
At the same time a global coupled version of the model is run to investigate the model's properties as a complete climate model, and to calibrate a slab-ocean version that will be used to estimate the climate sensitivity and the different role of Arctic amplification in a 1.5C world compared to a 2C world. This will complement analyses of flow regimes and weather-related extremes made in HAPPI.
