In collaboration with the University of California, Associate Professor Yu Kosaka of the Research Center for Advanced Science and Technology, the University of Tokyo, revealed that climate internal changes originating in the tropical Pacific have played a role as a "pacemaker" for global warming. ..
Due to global warming, the average surface temperature (global average temperature) over the entire globe has risen by nearly 1 ° C since before the Industrial Revolution.The tendency is said to be a step-like change that repeats an ascending period and a stagnation period every 20 to 30 years.However, in a normal climate change simulation (historical climate reproduction experiment), although a one-sided temperature rise on a XNUMX-year scale can be reproduced by using an external forcing force such as a change in greenhouse gas concentration in the climate model, the "stairs" of global warming can be reproduced. It was difficult to reproduce the timing.
This time, in a climate model, the research team conducted a "Tropical Pacific-Global Atmospheric Experiment" to forcibly match sea surface temperature fluctuations in the tropical Pacific with observed fluctuations in addition to external coercion.As a result of the simulation, we succeeded for the first time in reproducing the global average temperature change that has risen stepwise over the past 120 years with an accuracy that can be compared year by year.
Comparing this result with the historical climate reproduction experiment using the same model, it was found that the internal fluctuations in the tropical Pacific region have determined the alternating period between the warming period and the stagnation period as a "pacemaker" of global warming.
In addition, a method for removing the effects of tropical Pacific fluctuations from the observed global mean temperature is also presented.It has become possible to extract fluctuations by external force.The observed value of the global average temperature rise was suppressed to about 20 ° C compared to the beginning of the 0.9th century due to the stagnation period, but according to this method, it is estimated that the temperature rise due to external coercion has already reached 1.2 ° C. It is said that it will be done.
The research team will monitor the progress of global warming due to human activities in real time by using this method for the international goal of "controlling the temperature rise after the Industrial Revolution to less than 2015 ° C" agreed in the Paris Agreement in 2. It is supposed to be possible.
