Gabriela Narcizo de Lima
Dr Gabriela Narcizo de Lima's current research interests include urban climate, climate warming, water management and territorial planning. Her recent research includes "Urban Climatology in Brazil: An analysis based on an urban Climate System approach" and "Urban growth and its Impact on Climate in the Sao Paulo metropolitan area".
Without a global agreement to reduce emissions, the global climate situation is likely to worsen
The United Nations Intergovernmental Panel on Climate Change (IPCC) has released its sixth assessment report on global warming. The report presents five future global climate scenarios. These scenarios are based on a series of scientific calculations and studies on how humans will emit greenhouse gases. In addition to looking at changes in the Earth’s temperature, these calculations also look at changes in socio-economic areas such as population, urban density, educational levels, land use and wealth distribution. What do you think of these five scenarios? Which scenario do you think is most likely to come true? What can be done to avoid something worse?
The Fifth Assessment Report (AR5, 2014) of the Intergovernmental Panel on Climate Change (IPCC) has left little doubt about the human contribution to climate change. So much so that in its sixth report (ARG), IPCC experts concluded that, the anthropogenic origin of the rise in temperature is a proven fact with no precedent in the scale of recent changes on the climate system in the last thousand years.
This new report (Sixth Assessment Report - AR6) makes a point of a change in paradigms by showing that the evidence of extreme phenomena has been reinforced, besides, per every 0.5°C in the earth’s warming, there are perceptible increases in the intensity and frequency of storms, heatwaves, and hydraulic and agricultural droughts.
The AR6 assesses the results of the climate models that take part in Phase 6 of the Coupled Model Intercomparison Project of the World Climate Research Program. Such models include an improved representation of physical, chemical, and biological processes of climate models, as well as a higher resolution, compared to the climate models accounted for in AR5. Nonetheless, it is worth mentioning there are still differences regarding observations, especially at the regional level.
Another update that must be brought into our attention in the AR6, in relation to its predecessors, is a group of five new illustrative scenarios concerning emissions which permit to explore climate response to a wider range of possible futures, including different levels of Greenhouse Gas Emission effects (GHG), socioeconomic status, levels of climate change mitigation as well as changes in land use and variation in the concentration of pollutants in the air in the 21st century.
Some proposed scenarios include three main contexts:
● Low and very low emissions in which an emission reduction of GHG to net zero is expected by 2050, being followed by varied negative emissions of CO2. (SSP1-1.9 y SSP1 -2,6);
● Intermediate emissions (SSP2-4.5) in which GHG emissions are expected to remain close to today’s current levels until 2050.
● Very high emissions (SSP3-7.0 and SSP5-8.5) in which the duplication of current levels of CO2 is predicted by 2050 and 2100 respectively.
In all proposed scenarios in the AR6, it is predicted that a rise in global temperature will continue to happen along the 21st century, even exceeding 1.5°C and 2°C, unless GHG emissions are lessened drastically all over the world. In this sense, the sixth report makes note of quite a few of the changes generated by these emissions in the past -for which we are all held responsible- will be irreversible for thousands of years, especially those related to sea-level rise, impacts on the planet’s biodiversity, and major ice mass loss.
This new report draws our attention to the need to intensify climate change mitigation and adaptation efforts on the grounds that a massive, prompt and sustained emission reduction could help to limit the earth’s temperatures to 1.5°C. This in turn, could lead to a change in perceptible tendencies in a period of 20 years approximately.
The emission reduction pact discussed in Paris in the 21st Conference of the Parties (COP21), which later gave rise to the Paris Agreement, urged all signatory countries to make a commitment to limit the world’s average temperature rise to 2°C by 2100. However, in spite of international efforts and pressures from the nations most impacted by climate change, this agreement has been neither binding in nature nor concrete in target-setting for the reduction of emissions in every country.
The accomplishments of this conference were that each country would make a commitment to set their own goals and make their own plans to reduce emissions. To this day, however, it is observed that only a few of these goals have been achieved timely, six years after the agreement was signed. Such a situation makes it impossible to reach the final goal which is to reduce the global rise in temperature to a value lower than 2°C.
I might be taking a chance at appearing pessimistic –though perhaps realistic- but I believe that if we manage to encourage a more concrete international commitment at COP 26, to take place in Glasgow next November, we may be able to consider the possibility of keeping global emissions at similar levels as the current ones in this century. In this way, we would probably meet the intermediate scenarios of IPCC, thus limiting global warming to values lower than 3.5°C.
Editor Assistant Research Fellow: Xianglin Gu
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