The annual retreat of the tropical Tarija Glacier (Bolivia), suggesting warming may not be related to atmospheric CO2 increase

Abstract

We present here the longest known continuous annual moraine record extending from the XVIII century to the present, which portrays a very irregular retreat history of the tropical Tarija Glacier, in the Bolivian Andes. This study also proves for the first time in South America, the annual formation on these minor moraines, while field observations showed how these ridges form, substantiating the presented 258 year-long glacial retreat history. The annual retreat record is validated by correlation with Lake Titicaca surface level evolution: the highest ablation rate matches the highest lake level (1986–1987 yr). The glacial retreat also fits well with a large Pampean foreland lake level evolution (Mar Chiquita), suggesting this glacier reflects continental-scale climate trends. There is, however, no correlation with CO2 concentration curves. The glacier retreat suggest there were at least seven events of warming that lasted one to two decades, and none of these had any correlation to the greenhose gasses evolution. Besides, glacier retreat slowed down over the last three decades, in coincidence with the tendency of large lakes to a level fall, suggesting warming rate would also slow down. The departure of the glacial retreat chronology that worldwide is considered to be related to warming, from the CO2 evolution over the last three centuries, suggests CO2 does not contribute a primary effect on warming, as most models assume. Given some coincidences, we suggest climate shifts causing the irregular retreat of the Tarija Glacier, may be related to a delayed effect of solar irradiance indicating that the relation between solar irradiance and its impact on Earth´s surface systems needs to be better understood for a critical examination of the climate change paradigm.