Natural processes can accelerate the natural processes of anthropogenic warming could accelerate human-induced warming, which is not taken into account the UN Intergovernmental Panel on Climate Change (IPCC).
Illustration Jujupie.
If very briefly, the Earth is definitely hot. Despite the recent slowdown in the rate of warming, the temperature of the atmosphere today to 0,7 ° C higher than in 1950. The oceans also podnakopili heat.
And almost no doubt that much of this is due to human activity - primarily with our carbon dioxide emissions from the combustion of carbon-based fuels and deforestation.
The strongest warming recorded in the Arctic, where sea ice disappears, and the permafrost melts. Reduced sea ice is a record for 1450 years (according to some data, and for two thousand) rates. In 2012, installed a new antidostizhenie.
Rather, it is also the result of artificial climate change. Apparently, the warming of the Arctic will accelerate, and by mid-century, has anyone (except the very very special CR-readers) will not surprise the complete absence of ice in the Arctic Ocean in September, and the permafrost will thaw by 81%.
The increase is to say, the amount of energy in the air leads to more frequent extreme weather events, although in each case it is difficult to understand, it is caused by climate change or natural variability. The 2007 report expressed more clearly, saying that since 1970, the area of land covered by drought has increased dramatically, and by 2020, from 75 to 250 million people in Africa will suffer water shortages due to climate change. This time, the IPCC are not sure about the spread of the drought, and refrain from betting experts. Same with hurricanes and other natural disasters, Over the next decades, the changes at the regional level will depend on the natural variability.
In other words, the local climate is unpredictable.
Sea levels are rising faster and faster, since a warmer ocean waters expand, as well as the ice melts. The current rate is about 3 cm per decade, which is almost double the average of the XX century. By 2100, sea levels will rise by 98 cm (in 2007 predicted 59 cm).
Coastal communities are at risk of flooding.
Some scientists fear that natural processes can accelerate warming. For example, the melting of permafrost will lead to the release of frozen methane - a powerful greenhouse gas.
Considerable uncertainty as to how the world will heat up in this century, and how fast. Much depends on whether we can restrain the growth of emissions of CO2, as the gas remains in the air for centuries. In order to keep average warming below 2 ° C (with warming, as it is believed we can handle), it appears, make sure that the total emissions of the whole era of the Industrial Revolution did not rise above a trillion tonnes of carbon.
We are about halfway to this threshold.
But it became more defined role of mankind in climate change. The authors of the IPCC is 95% sure that human activity is responsible for the greater rigor of the warming of the past 60 years.
However, they admit that warming has slowed in 1998: This year is the warmest on record. This trend was not yet clear when the previous report was compiled (remember, he was released in 2007) and current climate models do not reproduce it. However, the slowdown has forced scientists to reduce projections of future warming. Before claiming that a doubling of greenhouse gas concentrations in the atmosphere (and this can happen by the end of this century) will lead to a warming of around 2,0-4,5 ° C. The present estimate - 1,5-4,5 ° C. Older models were talking about what is possible warming of 6 ° C, it is now considered unlikely.
In the absence of clear policy decisions on the global fight against climate change, the news can breathe a sigh of some relief.
Obviously, the skeptics who ignore the general conclusion that human activity is responsible for global warming, will seize the repeatedly mentioned uncertainty. Of course, they will notice that in some regions of the world in the late XX century, it was as warm as in the days of the so-called medieval climate anomaly (950-1250 years). Strictly speaking, it is a favorite theme of the deniers: if natural causes were once responsible for the warming, then and now the reason is they, and not the fact that mankind produces huge amounts of greenhouse gases.
However, the controversy about the temperature in the distant past can not undo the foundations of physics, which states that greenhouse gases trap heat and warm the planet, however hard you try.
Can we be sure that the IPCC is not missing anything important? Of course, we can not. For example, in a model that helps predict future state of affairs does not include some types of positive feedback, because they have not yet learned how to adequately describe quantitatively.
In particular, the report has been criticized for the fact that it does not address concerns about methane emissions from melting permafrost that will accelerate warming. In the end, as podcherkivaetKevin Schaefer of the University of Colorado at Boulder (USA), IPCC projections appear conservative and understated.
In the model, the IPCC does not include the possibility of rapid destruction of the Greenland and West Antarctic ice sheets and the collapse of the current system of ocean currents. The reason is the same: it is very difficult to estimate veroyatnost.Maykl Mann of Pennsylvania State University (USA) considers that the IPCC should not be afraid of low probability, if the events are a major threat. Policy makers need to know what is possible and such.
