At http://phys.org/print286532235.html … a lake in Iberia, in the Sierra Nevada, over 3000m above sea level, has revealed evidence of atmospheric polution around 2000BC. The researchers have blamed the polution on humans as they also seem to have found high lead levels in the Roman period. They are saying that metal smiths in the Early Bronze Age were responsible, on the assumption a great deal of bronze making was going on in Spain and Portugal. The paper is published in Science of the Total Environment, and from this we can understand why the human dimension is stressed beyond other possibilities. What caught my eye is that they say they also found evidence of landscape fires at the end of the third millennium BC – assuming once again humans had been responsible. The incidence of landscape fires around this time was part of the evidence that Moe Mandelkehr marshalled in support of his 2300BC event, which then leads one to think what exactly did they find in relation to lead poisoning. As the information comes from an abstract this is difficult to evaluate – but it may be important. Mandelkehr, of course, thought a heavy meteor storm was responsible, including multiple objects on a par with the recent Russian meteor. The evidence appears to be skewed by environmentalist tosh.