 Okay, I'd like to introduce Jennifer Wirtzell. She's from the ANU College of Physical and Mathematical Sciences and the title of Jennifer's presentation tonight is Reading the Rain in Rocks. Go away, come again another day. It's a familiar old rhyme, right? You probably remember singing it as a kid, your face pressed against the window, longing to go outside and play. But what if the rain did go away? For days, weeks, how about years? Decades. We know just from weather records of the last century that there have been times when the rains haven't come to places like India, China, Australia, just the last decade. Drought has led to water restrictions, famine, and in some countries loss of life. It's therefore useful to understand how rainfall patterns have changed in the past so that we can improve predictions of future rainfall. And that is why I study paleo-climatology. You might think of me as a climate historian. My job is to interpret the information held in archives in the natural environment so that I can learn how climate has changed before there were rainfall records. It might surprise you to learn that some of the best rainfall archives are actually stored underground. When it rains, the water trickles through the soil, and sometimes it hits a particular, though not uncommon type of rock called limestone. The water seeps through cracks in limestone, dissolving it as it goes, until it reaches the open space of a cave. And this is where something amazing happens, because as the water drips from the cave ceiling and lands on the cave floor, it actually starts forming rock again, growing and building into the magnificent formations we call stalagmites. And each layer of the stalagmite contains the chemical signature of the rainwater that formed it, allowing me to learn how much rain fell the year that layer grew. The subject of my research comes from a hot, humid, muddy cave on the very wet Indonesian island of Sumatra. My stalagmite, the one behind me, it's only about the length of your arm. But by drilling down the center and measuring the chemistry of these tiny powder samples, I have unearthed 16,000 years of rainfall history, which tells me Sumatra has had its fair share of dry spells, some lasting over 100 years. Together, with more of these incredible cave records from around the world, I can start piecing together global cycles of drought and rainfall in the past. And that is the key to answering the question of whether the rain will go away in the future.