 There is a lot of evidence that recent warming of the planet is caused mostly by human emissions. This evidence is so strong that an overwhelming majority of climate scientists accept that the warming seen since 1950 is mostly man-made. However, there's a certain climate change myth that chooses to ignore all this research. The myth claims that the recent warming is just a continuation of natural processes that enter the little ice age. Here we'll see that the evidence shows that natural factors were indeed important to begin with but since 1950 human influences have become dominant. First, what was the little ice age? Well, it lasted from about 1450 to 1850 although some scientists think it started as early as 1250 at the end of the medieval war period. Just how cold was the little ice age? In Europe, Central Asia and North America the average temperatures are now 1°C that's about 2°F higher than the temperatures that prevailed during the little ice age. This warming might not seem like a lot but it has been enough to cause the majority of the world's glaciers to shrink. Most of the rest of the world has warmed up since then with the exception of small areas that are slightly colder than they used to be for example, off the southern tip of Greenland. Glaciers advanced during the little ice age, not only in the Alps and Rocky Mountains but also in New Zealand and the southern Andes although the exact timing of these advances varied but after that as the cool period ended glaciers nearly everywhere started to retreat. The little ice age had its best known historical impacts in Europe so mud weather patterns in North Atlantic made the already cool climate there even worse in some years. There were some bitterly cold winters and there were also some very wet years that led to crop failures and famines. Famously, river Thames in London froze over and frost fairs were held on the ice. Despite cold average temperatures the hard freezing in the Thames was still a rare event it froze over thick enough to hold a frost fair just 21 times in 300 years. What do we know about what caused the little ice age? First, small changes in the tilt of the earth helped cause a gentle decreasing trend in temperature over 5,000 years. The rate of cooling was about one-fifth of a degree Celsius that's about one-third of a degree Fahrenheit per thousand years. The little ice age occurred towards the end of this long slow decline. It ended when temperatures started to go up sharply after 1850. Second, there were at least two large lows in the output of the sun which we call the Spira and Monde Minima. Third, there was an unusual number of really big volcanic eruptions that through small particles highens the atmosphere. These acted like little mirrors that reflected sunlight back into space and cooled the earth for a year or more afterwards. An example was the huge Mount Tambora eruption in 1815 which caused what came to be known as the year without a summer. Scientists are not completely sure about the exact size of the cooling effect that volcanoes and solar lows had on the earth but even so, a range of calculations for the northern hemisphere shows a very good match with what the evidence suggests the temperatures were. Researchers estimate the temperatures of the past by analysing records like tree rings, ice cores and the growth bands of stalactites in caves. In this graphic, the red and blue lines show the calculated values and the grey shading shows the range of reconstructed temperatures. The long-term trends match very well including following the rapid upward trend into the 20th century. Volcanic eruptions and solar variations carried on after the little ice age but they were generally smaller and were dwarfed by ever bigger human influences. More people and growing industries produced more and more greenhouse gas emissions. This graph made with the data taken from the recent IPCC report shows the relative importance of volcanoes in black and the sun in green as well as natural variations which are shown in orange. These variations are mainly caused by fluctuations in ocean currents like El Niño. Note that the natural factors sometimes cancel each other out and they do not show any lasting trends unlike the steadily climbing human influence which is shown in red. When we add together the natural and human factors and overlay the natural variation as the faint background that jumps around we can see that it would be hard to distinguish a clear separation between human and natural causes before about the 1930s. Now let's compare these factors with the thermometer record. The monthly temperatures are shown here as a grey wiggly background and a smooth version of this is shown in black. The match is good when we look at all the factors combined but it's terrible if we exclude the human influences. Back in 1914 it would have been possible to argue that the recovery from the little ice age was almost entirely natural but now, 100 years on, it's clear that humans are playing the major role and by far. To claim that what was once arguably true 100 years ago must still be the case today is to introduce the fallacy of jumping to conclusions which is to say that just because a factor was once significant does not mean that it's still important. Times changed and over the past 100 years human influences on the climate have grown enormously and they continue to grow. They are now the main factor causing the warming of the earth.