Sentences with phrase «human aerosol»
The phrase "human aerosol" refers to the airborne particles that humans release when they talk, cough, sneeze, or breathe. These tiny particles can carry germs and viruses, which is why it is important to wear masks and maintain distance from others to prevent the spread of illnesses. Full definition
We have recently discussed several papers which have found substantial global dimming as a result of increased human aerosol emissions from 1950 to 1980 and 2000 to 2010.
skepticalscience.com
There is a fairly large degree of uncertainty in these figures, primarily because the magnitude of the cooling effect from human aerosol emissions is not well known.
And exactly how much global warming is being offset by human aerosol emissions?
And exactly how much global warming is being offset by human aerosol emissions?
So Nielsen - Gammon is correct to note that some of the slowed surface temperature warming over the past decade can be attributed to La Niña, although there have been other influences at play as well, such as human aerosol emissions.
The reason greenhouse gases can be (and probably are) responsible for more than 100 % of the observed warming is that other factors (mainly human aerosol pollution) have caused cooling at the same time.
Note that while the BEST approach is based on correlations, they are correlations of variables with known causal relationships (i.e. an increased greenhouse effect is known to cause global warming), although they do not appear to have considered some important influences like human aerosol emissions or the El Niño Southern Oscillation.
All of these studies find that humans are responsible for close to 100 % of the observed global warming over the past 50 years, and human greenhouse gas emissions are responsible for close to 150 % of the observed warming, with human aerosol (sulfur dioxide - SO2) emissions offsetting approximately one - third to one - half of that greenhouse warming.
It didn't include the warming effects of other greenhouse gases, or the cooling effects of human aerosol pollution, but fortunately for Broecker those two effects have roughly canceled each other out over the past 40 years.
If we add in the warming effects of the other long - lived greenhouse gases, the best estimate rises to 1.22 °C surface warming caused by human emissions (we've only observed ~ 0.8 °C warming because much of that has been offset by human aerosol emissions).
Huber and Knutti (2011) found that human greenhouse gas emissions have caused 66 % more global warming than has been observed since the 1950s, because the cooling effect of human aerosol emissions have offset about 44 % of that warming.
Human aerosol emissions are also offsetting a significant amount of the warming by causing global dimming.
Some question remains as to how much of the temporary slowdown in surface warming is due to human aerosol emissions, how much due to ENSO, how much due to heat being transferred to the deep oceans, and so forth.
Greenhouse gases can be attributed to about 0.9 °C of this warming, but it has been partially offset by about 0.3 °C cooling from human aerosol emissions.
Human aerosol emissions are also offsetting a significant amount of the warming by causing global dimming.
Huber and Knutti (2011) found that human greenhouse gas emissions have caused 66 % more global warming than has been observed since the 1950s, because the cooling effect of human aerosol emissions have offset about 44 % of that warming.
Further, Christy did not remove the effects of human aerosol emissions, solar activity, or a number of other factors which had a net cooling effect between 1979 and 2010.
Every such attribution study has been consistent in concluding that humans are driving global warming (Figure 5), with greenhouse gases causing more than 100 % of the observed warming because much of that is offset by the cooling effects of human aerosol emissions, which block sunlight (Figure 6).
The main messages from these two figures are that natural temperature influences can not account for the observed global warming, especially over the past 50 years, and that greenhouse gases have caused more warming than has been observed, meaning that the net non-greenhouse gas effect is a cooling one (mainly from human aerosol emissions).
Human aerosols are only going to be significant with China and India using more and more coal.