Climate Science already old physics
The impact of carbon dioxide on climate was invented already more than hundred years ago by a Nobel winning Swedish physicist Arrhenius. He could not imagine the magnitude of the current use of fossil fuels. The risk of man-made climate change was understood by the meteorologists in the 1960s and 1970s. The World Meteorological Organization organized the First World Climate Conference in 1979 and decided to establish Intergovernmental Panel on Climate Change (IPCC).
The IPCC, hosted by WMO in Geneva, produces extensive assessment reports based on peer-reviewed literature. The authors and the reviewers are world leading scientists, and they are selected based on their scientific merits. So far IPCC has published five large assessment reports and several special reports.
The most recent report was dealing with 1.5 degrees warming, which is the lower limit of the Paris Agreement. The key messages of the report may be summarized as follows:
- We have already reached 1.0 degrees warming, growing amount of natural disasters related to weather, 26 cm sea level rise and melting of all glaciers as well as the polar sea ice
- To reach “safe” 1.5 C warming the mankind should reduce the use of fossil energy within the coming five years and stop the use of fossil fuels by 2050.
- Economic and technical means to achieve 1.5 C exist.
What is important: fossil energy, forests or food?
At the moment about 85 % of the world’s energy is based on oil, gas and coal, and only 15 % is produced by carbon free sources nuclear, hydro and renewables. To reach the targets of Paris Agreement one should replace the energy usage with the latter three. Carbon dioxide is the challenge number one due to its very long lifetime up to thousands of years influence on climate. CO2 has been responsible for two thirds of the warming so far, out of which about 90 % comes from fossil energy use and the rest from deforestation in especially tropical areas.
Methane with lifetime of 12 years is responsible for 17 % of the warming with main sources in tropical wetlands, rice paddies and cow herding. Methane is stored also in Arctic permafrost and sea bedrocks, but so far no major outbreak has been observed. By avoiding rice and cow cattle products fairly small emission reductions may be achieved.
To mitigate climate change the absolutely biggest challenge is to cease using fossil sources of energy. Forestation is also a good way to mitigate, but it will never be efficient enough to compensate the warming caused fossil energy usage. One should also distinguish between renewable boreal forests and the non-renewable rainforests while considering the forestry sector as mitigation mean.
Climate change is already visible
The impacts of climate change are very visible. Last four years have been the warmest since 1850, and 20 out of the 22 warmest years have been observed this century. There has been an increase of flooding, storms, heat waves, drought and forest fires. The biggest economic losses have been caused by tropical storms (hurricanes, typhoons and cyclones) and flooding. Biggest human casualties have been related to heat waves and drought.
93 % of the excess heat produced so far has been stored to the oceans, which have warmed by 0.5 C contributing also to sea level rise besides melting of polar and mountain glaciers. Melting of the biggest glaciers in Greenland and Antarctica is a very slow process. If mitigation fails, sea level rise of the order of 1 m/century is expected to take place up to thousands of years.
The warming has been largest in the Arctic, where the warming has exceeded 2 C due to boosting effect of the melting of snow and ice. About 75 % of the Arctic sea ice mass has disappeared during the last 30 years. The warming of the Arctic has affected the weather patterns in the whole northern hemisphere favouring more stagnant weather patterns, like cold spells in winter and heat waves in summer.
According to International Monetary fund climate change has already had a negative impact on Southern hemisphere and tropics, and a positive impact on high northern latitudes. Those are related to changes in rainfall patterns (drought/increased rain) and temperature changes (impact on agriculture and forests).
Hope still exists
The awareness of climate risks is very widely understood by decision makers, private sector and citizens worldwide, which has enhanced the willingness and means to solve the problem. Especially the European countries have succeeded in emission reductions, Australia has already achieved its Paris pledges, USA has achieved about half of those and many countries are having ambitious mitigation plans. The price and attractiveness of renewable energy have been very favourable. Low-emission and electric car manufacturing has increased as well as energy saving means for cooling and warming of buildings.
Consumers have become growingly aware of the climate friendly products and climate friendly food is becoming popular. Cycling and public transportation are growing.
United Nations secretary general is hosting a Climate Summit in September 2019 for heads state to raise the ambition level of climate mitigation and adaptation. Many countries and private sector are preparing new ways to tackle the climate problem. The problem can still be solved.
Prof. Petteri Taalas
World Meteorological Organization (WMO)