Two F-15E Strike Eagles wait to receive fuel from a KC-135R Stratotanker during exercise Red Flag 15-1 on their way to Nellis Air Force Base, Nev., Jauary 23, 2015. The F-15s are assigned to the 4th Fighter Wing. U.S. (Photo by Airman 1st Class Aaron J. Jenne/Reuters)

A garbage collector, with his horse and cart, prepares to unload rubbish at the municipal dump in Nezahualcoyotl, on the outskirts of Mexico City, February 18, 2015. Hundreds of horse or donkey-drawn carts will disappear from the streets of a municipality in the state of Mexico, located on the outskirts of Mexico City, and will be replaced by motorized vehicles, local authorities said. (Photo by Henry Romero/Reuters)

In this January 27, 2015 photo, penguins walk on the shore of Bahia Almirantazgo in Antarctica. Antarctica “is big and it's changing and it affects the rest of the planet and we can't afford to ignore what's going on down there”, said David Vaughan, science director of the British Antarctic Survey. (Photo by Natacha Pisarenko/AP Photo)

Members of a music band rest before the procession of “Nossa Senhora da Boa Viagem”, in Constancia April 6, 2015. This benediction has been held annually for about 200 years. In the past, goods were transported by the Tagus river in small boats to Lisbon, 100 km south. The sailors, as the navigation was dangerous, blessed their boats every year during the festivity of “Nossa Senhora da Boa Viagem”. (Photo by Rafael Marchante/Reuters)

A child wades through the mud next to a grave inside the flooded cemetery in Los Loros town, April 7, 2015. The death toll from heavy rains and flooding that battered Chile last week has risen to 29, with another 150 still missing, according to authorities. (Photo by Ivan Alvarado/Reuters)

Thai officials inspect counterfeit watches before destroying them at Khlongluang Transportation Station in Pathumtani province, on the outskirts of Bangkok April 9, 2015. The counterfeit goods, which included piles of CDs, DVDs, handbags, clothes, brand name shoes, cell phones, caps, glasses, computers, cosmetics and watches are worth over 3.7 billion Thai baht ($ 115,790,901), according to local authorities. (Photo by Chaiwat Subprasom/Reuters)